Q:

Why closed, why not migrate it? 

I just saw this question: https://stackoverflow.com/questions/12339053/i-am-not-my-username-why-asda-and-other-big-companies-use-it
It is marked as closed.  Why is it not moved to appropriate Stack Exchange site? 

A:

Only moderators can migrate it to most of the Stack Exchange sites (the close menu has only a few options, such as meta, programmers and a few others.) 
You can flag it for migration if you want a moderator to look at it.  But that should only be done to questions that wouldn't be closed on the other site for some reason (bad quality, subjective).