I am not sure it's the right place to post this as it's common to all Stack Overflow sites. I suggest sorting sites by user reputation and then alphabetically in the all-sites list of the Stack Overflow button.
This list is now sorted by reputation first, and then alphabetically to make it easier to find the site you are looking for.
The list is sorted, it just hasn't kicked in for you yet based on your reputation.
Sites where you have > 200 reputation will be sorted by reputation, highest reputation accounts at the top.
Sites where you have < 200 reputation will then be listed in random order. e at the top.