Wasn't Taegoon charged with use of drugs or something like that? Pretty sure I read something like that around. Plus, he did a bit of acting some time ago, didn't he? Maybe he just liked it better than singing.
AFTERSCHOOL released Flashback not too long ago and I already need them to give me more amazing music. INFINITE, JOO, Seo Inguk, PHANTOM, Chaeyeon, IVY, Andamiro, Outsider, Hwanhee (he's in the army though, so it's going to take a while), An Jinkyoung, JYJ, Jaejoong (just give me that solo album ;-;), Kahi, Nine Muses. I'm pretty sure there's more to be added to my list, I just can't think of them right now.