There have been a couple times so far where someone has requested me to have one of my works displayed in a group gallery. Even though it isn't all that often, I've declined every time. I'm not against groups on DA or the idea of having my art in one. After all, that would easily get me more attention. The only real reason I decline these requests is simply out of lack of involvement. It might also be a modesty thing, but I don't really use DA enough to care about gaining any traction. I've even considered shutting down this account a few times, mostly due to the questionable ToS changes (nobody has the right to redistribute your work without permission, regardless of content).
So if you asked me to have one of my uploads presented in a group gallery, don't feel bad if I decline. I just like to stay low around here.
Reading: Sam & Max: Surfin' the Highway
Playing: Jedi Knight: Dark Forces 2