There are several reasons.

At least Tear is currently impossible to get into extras/extras-devel. Unless Vala is currently supported with custom vapis and some changes to system includes.

Another thing is even though I'm not sure Tear is stable enough for mass usage, people are willing to try it and are afraid of extras-devel, and it seems the already existing qole repo is good for easy installation. The only lib in it that exists in extras-devel is libidn11 and its taken from there.

Extras is out of the question yet.