There are many questions (including one of my own) that fall into the category of "Why did 
X company do Y?" Should these questions be removed for not being constructive? Examples: http://ux.stackexchange.com/questions/35714/ios-multitasking-closing-is-poorly-designed http://ux.stackexchange.com/questions/34872/is-there-a-reason-why-ms-outlook-express-puts-data-file-in-a-hidden-folder
http://ux.stackexchange.com/questions/35024/why-are-nested-elements-scrolled-to-the-opposite-direction
http://ux.stackexchange.com/questions/34650/what-reason-could-nintendo-have-had-for-putting-the-a-and-b-buttons-the-wrong-wa/34677#34677
http://ux.stackexchange.com/questions/8980/what-is-the-reason-for-concave-round-buttons-in-elevators?rq=1
http://ux.stackexchange.com/questions/8560/what-is-the-reason-behind-the-sign-icons-with-buttons
http://ux.stackexchange.com/questions/6210/what-is-the-reasoning-behind-grayscale-icons

That's just a few of a **MASSIVE** population of such questions.

I think what needs to be determined is: Is UX only a place for people to ask questions about prospective/existing designs, or does UX also foster discussion about famous/classical design implementations/commonalities.