There are two questions on this site tagged with questions, and 10 questions tagged asking-questions. These tags should probably be merged.
1 Answer
asking-questions is a subset of questions. The latter may be about other question activities - answering, closing, editing, deleting, voting, etc. - or about questions in general.
For example, the tag combination questions+voting represents an entirely different subject area from answers+voting.
In addition, there may be feature-request posts that are about questions. If these were to be tagged asking-questions instead, then it would have a different connotation. The latter really implies more of a support request.
Admittedly there's a bit of a gray area (and of course there's nothing wrong with having both tags on the same question) but there are clearly cases when a meta question should have one tag and not the other.
At the end of the day I'm inclined to follow MSO's example; they haven't merged those tags despite quite a bit of overlap and high volume.