When flagging a question for migration, only a very short list (dare I say even a tiny list seeing all the wasted white space around it) of other StackExchange sites is proposed (namely Meta, StackOverflow, SuperUser and ServerFault).
Why is it so?
When searching Meta, I've found older posts dealing with the creation of this list during the Beta era, but nothing explaining the reason behind this limitation.
Personally, from an accessibility point of view I would understand to put most frequent sites as they are now, and below having a drop down list to select another less frequent site among all the other StackExchange sites.
However, current interface seems to willingly put a strong limitation on questions migration requiring the user to close the question here to recreate it from scratch on the other site... It does not seem practical for me, and I do not understand the reason behind such a rule.