Because a dirty free hand sketch is infinitely sexier than a sketchup rendering. Anyone can paste together something in CAD or CS... 

a sketch is not "personal design process" - it can convey an idea in 2 seconds; until any digital tool can do that, hand sketching will still be the first option.

If you really want to impress people, sketch upside down across a table from them. It just takes some practice.

Sketching also triggers different parts of the brain, so you might even come up with a (better) solution you'd never even conceptualise when drawing on a computer. There is something magical happening when you put a pen or pencil on a piece of paper and start scribbling. Also, how do you scribble in CAD? That being said, I'm horrible at sketching and whatever I sketch is often out of proportion, generally ugly and not meant to be flaunted or seduce clients with. It is a personal design and engineering tool for me that helps me clarify my thoughts and identify problems and solutions.

I wish I was better at sketching (and hand drafting).  Most clients don't appreciate it as much now. They like hyper-realistic renderings because it gives them a more realistic look and feel of the project. A hand sketch rendered with color pencils or markers or water color still wins for me. Like this one:

Eye-hand coordination, the basis for all human development, entirely lacking with computers.

Keep sketching and you will get better. Life drawing classes help a lot - with drawing and more so with seeing.

It's not only eye-level renderings, but don't forget diagrams, plans, sections, elevations, details... all the 2D stuff.

Personally, I think there's a lack of understanding in the development of technology in the older generation of architects. These days there's the possibility of drawing using your phone and even computer with a drawing tablet.

In saying that there's a benefit in drawing with your hands as an architect there's a thinking process that develops in the mind when you settle and take the time to draw.

I fond of drawing! The best thing is making my imagination turn into a real thing, a piece where it only came to my mind and no one did. I like drawing ever since a child, I want to elaborate things to let them see my perspective.

When I didn't find the drawings I really want to see, I draw them. Even though it turns out different than I imagine sometimes but in the end, I still enjoy its company.

Making characters and see how they go through their lives, drawing things to view what is your perspective and how you'll change or keeping it like it was what you viewed.

Learning new things, and observed the surroundings.

I love drawing because I know in the future, I'll see it with my own eyes the picture I've always imagined and I can keep going and grow further.

Hand sketching allows you to work through ideas in a loose and free manner, not constrained by the (often) limited tools available in software.  Buildings that are the direct result of a software tool constraint are sad...the push pull in sketch-up is primary aesthetic driver for most of the terrible developer modern buildings from the early 2000's to present.  

There is a book I love from Architect Susan Piedmont-Palladino called "How Drawings Work", and she tackles this beautifully! In short, computer drawings can be amazing tools for conveying your idea and providing instruction for how to build. But it should not replace sketching.

Sketching has a level of uncertainty to it that can be incredibly useful when presenting to a client. You can make gestural marks which only suggest an idea, but leave open the possibility of change.

Computer drawings express a level of finality that might not be true. The hard lines make everything seem thought through and worked out. Sometimes that level of detail is actually bad for a presentation.

If your goal is to meet with your clients and give them options...possible directions yet to be explored...and to include them in the design process rather than show them your finished idea, then sketching is the eternal solution.

I wrote a bit about this in the following link! Enjoy.

3 Reasons You Must Sketch as a Designer

Sketching is faster, more direct, can be done nearly anywhere, doesn’t require a plug or a printer or a screen etc. I send hand sketches all the time to GCs, snap a photo, saveas to the server folder for future reference, takes all of 5 minutes, as opposed to spending 30 minutes opening up revit making a new sheet etc etc. besides if you can sketch something by hand you can apply that to literally any software out there. If you only know softwares you’re ruled by the commands you’re familiar with. The pencil is limitless, buttons on a screen are confining. Plus sketching in front of a client always seems to wow them, and is maybe one of the few instances where they actually realize the value and skill of an architect first hand because it’s something they absolutely cannot do. A client can however, go to floorplans.com or something similar and therefore thinks they can layout plans...draw them a wall detail in 30 seconds in a board room and boom they realize there’s a little more to it.

CAD is the illusion of being able to draw. It is like a carpenter who can only use power tools but can’t make a cut with a handsaw or drive a nail by hand. 

But I have a power nailer! I don’t need to nail by hand. 

And thus you will split the wood indiscriminately, miss the framing when nailing off sheathing, be unable to nail odd conditions with the vast plethora of tricks of the trade like nailing around corners by bending the nail into a curve, and so on.

To put things bluntly, hand sketching is the shit.

Your ability to draw out things in front of a client will always be a critical skill for anyone who wants to design.   The medium that is used for this is open to personal preference.  

Sketching is just another tool to convey design thinking, and communicating intent. It isn't as simple as saying that sketching is the end all be all, but fundamentally it is a basic skill that needs to be mastered by any professional in the design field. 

Sketching is key! It's way faster to sketch out ideas on paper- erase/go over/use trace layer paper to see different layout without maneuvering software/iPad, I like it for Preliminary design. That way when I'm ready to transfer to digital I can just trace right over or already know the layout of things... I had this one boss who could not sketch and every time he would meet with clients to alter plans - the changes would look like chicken scratch :/  Now if he could sketch right there on the spot, that would be great.

I think that sketching great buildings in the field is really important.  I ask all my students to keep a sketchbook and to spend time each week sketching architecture in the field, and doing measured drawings of details.  There are a couple of good  reasons why this is important. 

First, keeping a personal record in a sketchbook of the details of great architecture is an  important reference.  Also, simply spending the time to draw great buildings makes you spend lots of time looking at them, and soaking in the nuances of the architecture.  That's the problem with photography.  You pull out your iPhone and snap a photo, and you move on.  But you don't take the time to really SEE it.  There's no investment in it.  But if you sketch it, or better yet, do a measured drawing of it, you spend time carefully looking at the shapes, the proportions, the way light and shadow cast upon it.  You see things you are apt to miss in a photo.

Every weekend I sit on curbs in San Francisco and sketch. Sketching Victorians on sloped streets is a real workout, but makes my architecture sketching a lot easier - This is a sketch from Paul Madonna " All Over Coffee" book - he would just wander, sit on a folding stool, and sketch, then use india ink washes. 

I’ve always valued drawing, in school and even now in practice. Over the last 2 years I’ve been involved in the design studio at a prominent university in South Africa.
In my experience, students who can sketch their ideas are able to critique their own work much more successfully than those who use other mediums. They develop the confidence to explore more ideas and quickly.

I recognise that in my context I focus on the process of the student’s work, more so than the product. But it’s good to keep in mind that if we don’t prioritise sketching in our industry, this too will be lost from the architects arsenal; and given to yet another discipline.

I think despite the fact that CAD software are fast but their accuracy makes limitations while the designer is still thinking. The loosey character of the sketches lets the designer to unleash the creativity.

Despite the fact that I use CAD software is the detailing phase but we heavily benefit sketching while improving and rethinking on the design in our practice.