You said a dirty word: w*y.
A large part of the Stack Overflow community hates it when you ask why something happens. This phenomenon is specific to Stack Overflow, I haven't seen it on other Stack Exchange sites where I participate (such as Unix & Linux or Security, to stick to technical fields). Those sites are ticking just fine, producing valuable content retaining experts, having markedly less strife around than on SO. So it's definitely U&L and Sec.SE doing it right, and SO doing it wrong.
So why (look, SOpedians! I said “why”!) is it so bad to ask why? Here's my $0.02 sociological analysis. (Warning: if you paid that price, you've been swindled.)
To ask why is disruptive. “Don't make me think” is well-known advice in user interface design, and why is all about making one think. To ask not only how to do this but why is this so demonstrates curiosity, a search for more, a willingness to outreach yourself.
Yet such propensity is common among artists, scientists and craftsmen. Aren't programmers craftsmen?
Some are, some aren't. I think among the ones who are, a second factor is at play: the myth of the hacker. A hacker does not write a program: a hacker exudes a program. If you need to code by a spec, you aren't a real hacker. To ask why is to second-guess yourself, because it puts the design into question — but the design must flow.
So the yin and the yang of the programmer conspires to reject the idea that there may be intelligence in the design. It's all in the execution, baby!
Why was it done that way? Who knows? Who cares? I don't want to care! Don't make me think!
Of course, if you start thinking about what you're doing, if you value understanding over doing by rote, that does make you a better programmer. But that's neither here nor there. Stack Overflow is not really about good programming questions and answers. It's about popular questions and answers. Help me get a fish plzsendtehcodez kthxbye. Start asking why, and that's a question that requires more than two br*in¹ cells to answer. That takes thinking, and knowledge! No avenue for quick rep! No, that cannot stand on SO.
Once upon a time, there was no “non constructive” close reason. There was, instead, “subjective and argumentative”. The close reason was renamed because people tended to be overzealous and close any subjective question. “Not constructive” was supposed to make it explicit that the problem was questions that did not call for “answers to be supported by facts, references, or specific expertise”. The gist of it is that a bad question invites answers that say “I like the red one”, whereas a good question invites answers that teach you something — why the proposed solution is a good one.
This hasn't worked: a question that asks why is rather likely to call on “specific expertise”, yet “non-constructive” is used as a “this is subjective” close reason. Not that why is particularly subjective — it's only subjective if you don't know why — but why does look subjective if you don't know why, and for any given questions, most people don't know why.
It is, sadly, difficult to get a why question accepted on Stack Overflow. Calling on specific expertise is frowned upon. My subjective impression is that this problem is getting worse over time: the SO community (or at least, the part that takes interest in its governance) is predominantly interested in volume over quality, and SO has such a volume of questions that it cannot fail to be successful by that measure. The flip side of the coin is that most questions are crap. Of course, 90% of everything is crap. Yet it saddens me that SO is rejecting some of its best elements. I hope it won't take all of SE down with it.
¹ Also a dirty word on SO, which explains why mentioning Br*infuck by name is risky on MSO.