Chat rooms can be associated with meta sites, as discussed, for example, here: Why can meta sites be parents of chatrooms? (In this post you can notice that there were some recent changes concerning where the rooms associated with metas are displayed.)
So I wanted to test whether it is possible to create a new room associated to meta. To my surprise, this was possible only for some sites. For example, if I start to type "math", several metas are offered. When I start to type "history", I am only offered main sites. See the screenshots below.
This experiment suggest that only the meta sites for which at least one room already exists are offered. I have listed metas which had a chatroom here (at the time of posting that question).
Why only some metas are offered in this dialogue as possible room parents? Is it on purpose?
I do not think it is a big deal. But I can imagine a situation where associating room with meta might be useful. For example, imagine that community around some SE site wants to have two separate rooms: A "main chat room" for general discussion about the subject of this site and a "meta chat room" for various "janitorial" tasks (like closing, reopening, retagging, editing, flagging and advice related to this - which is somewhat separated from the the subject of the site, more closely related to maintenance and moderating of the site). It is might understanding that at least one room associated with a site, be it a main site or meta, is kept alive, even if there was no activity for 14 days. (And this comment by Marc Gravel seems to confirm this.) So the advantage of this arrangement would be that the "janitorial" room would not be frozen even if there were some period of inactivity. (Assuming it is the only room associated with that particular meta sites.)
Perhaps you can think of some other scenarios when having meta as a parent room might be useful. However, this is not that important for main main question - I am simply asking why the dialogue for room creation behaves in the way described above and whether it is status-bydesign.
Here are the screenshots:
