I've never done a single sidequest that doesn't unlock a feature since I started the game. I want to do them just to clear up the maps, but I have so many to do that I know I'll never do them.
I do them on alt jobs to pass the time, like if im queuing for something that is 10m+, il clear out some sidequests on a alt for some free xp and to play the alt job a bit /shrug
This is what I do on DPS queues. Now that I finished all of them I guess I'll just take a nap or something when I queue up.