Firms work within state employment law. At-Will employment explained here.

As an employer, better to say nothing.  Terminating a member of staff generally isn't over one single thing or even a list of a few reasons. If it is simply out of work, that's easy.  If it was you, best to move on.   Sorry.

++TED,

Explaining it in today’s environment is a good way to get sued.

Besides the fear of legal action should the firm provide a problematic answer, it's just not good in general for the firm's purposes moving forward.  

First, the firm may want to leave the possibility open of hiring the person again in the future.  Think about it: if you're laid off because of lack of work, and they tell you "well you were the one laid off because you were the least productive" or "you just didn't click as well with the firm's culture than your cohorts do", or whatever, that may leave you feeling defensive or resentful.  If it's just that they don't have enough work - which is by far the most common reason for layoffs - and somebody just has to go, then they may have had a real struggle coming up with a reason to pick anyone to go, and they really may have no reason that is so strong that they wouldn't want you back if things pick up someday.

Or, if they tell you that the layoff was based on your relative seniority or lack thereof, or of lack of tenure, or whatever, and then that reason becomes known to other staff, then whoever is next in line based on that criteria is likely to become very worried and possibly jump ship preemptively.

Or as you've hinted yourself, in a firm with multiple partners sometimes there isn't unanimous agreement as to whom to let go.  In that case they may be reluctant to discuss it or have agreed amongst themselves not to, because doing so could reveal dissent.

I've been on both sides of this - the one doing the layoffs, and the one being laid off.  Either way it's an unpleasant situation that neither party wants to be in. Trying to get an answer about this months later from a former employer is bad form - they don't have to give you any answer and you're just prolonging unpleasantness by asking.  I do understand why you want to know, but if you're really compelled to ask anything, you might get more information if instead of asking for the reason you were laid off you ask for constructive advice about where to focus your efforts at improving your skills in the future.  

Having been laid off numerous times, the answer to why you got "picked" comes from within

Ask yourself instead and lo and behold, you will have answers - holes in your knowledge?wasn't thorough enough with those red-lines? slipped out too many times too early? wasn't a good cultural fit?- didn't eat lunch in the office when everyone else did? Or not being up to speed on Dynamo or grasshopper, not knowing Revit? - or in my case, not knowing autocad? Not being up on codes? Insufficient A.R.E. and IDP progress relative to peers? Poor writing skills? Not following up in a timely fashion with consultants?

Ask yourself why - don't ask anyone at the firm that laid you off, they can't say

Point being, is to do what it takes to not be in a "position of risk"

as I have said in many other posts, read Brian Tracy's "No Excuses" I read this book every day and have read it 3 times so far.

Think all should back off - sometimes getting laid off is random. And most times its for the better.

Just like many who go through a long marriage then ready to move on.

https://youtu.be/w4xPv9x518Q

TED is right, each time I got laid off, or when a temp gig ended, I always went on to something better anyway within 2 - 3 weeks. One should never see their career as within one firm - its really an aggregation of experiences and education.

kids listen our man Xenakis, a real engineering genius and avant garde composer, well not this Xenakis, knows his shit about losing his job and he is still alive so listen.

Alphabits,

that was an excellent response. that answered the question better than someone saying get over it. I actually did deserve to get laid off, i knew i gone the minute they announced it. I could not see anyone else that should be laid off in my place. But I valued things there that i will never devalue,  just so i don't miss them and can get over it. I do understand that they don't have to give me anything. but if you had a long standing respectful relationship and handled yourself very well during the layoff then just asking shouldn't start a fire fight.  but it might. I know that they would lay off when the chance arrived based on clashes or differences of opinion that were having to much negative impact on the work. or sometimes you half to clear out a level to make way for the next group.

Again thanks for the extensive and thoughtful response. I'll just have take what i value and make the best of it, along with a lot work to find a similar environment. especially if competes with them, now what's healthier than a little competition. 

Xenakis , thanks for the Book suggestion.

While there can be any number of legitimate -- and illegitimate -- reasons inhibiting a firm from providing an extensive explanation about why one person is let go and another person stays employed, you can rely on the notion that firms always try to keep their best - and most productive - employees. 

If you are one of those who lost your job (my sincerest condolences) then you need to search your heart to determine what aspects of your own performance left you in that unhappy position. Were you spending too much time surfing the web and posting on Archinect? Did you fail to show initiative, keeping to yourself and distantly pursuing your work in silent isolation beneath headphones? Were you making the same mistakes over and over again? Were you cavalier about office hours and office policy? Did your personality lead you into constant conflict with co-workers and supervisors? Were you simply not very productive?

I have no reason to believe that any of the above represent your particular situation. However, something in your time on the job led the firm to value other individuals over you. If you're objective with yourself, you certainly can identify the causes on your own, and -- with some effort -- learn from those mistakes so your next job will be more successful.

Good luck.

It's always good to let your former employer that you appreciated the experience and ask if there are aspects of the work that you could improve upon or experiences that would make you a better employee for someone like them.  it's a small world in architecture and it's best not to burn too many bridges; the questions may help you land the next gig too.

good luck, it's crappy being let go, but keep your head up and move on.