Maybe it has to do with the length of the animated feature. Seems to me that DC caps their animated movies at a hour & twenty minutes, maybe a hour & a half. Ya get a family of four - parents & two kids - into the theater, they've shelled out thirty-five to forty to be there, for not very long at all.
On the other hand, ya release the same movie direct to DVD/blu ray, and for half the cost, the same family gets the movie to watch as much as they want.
Now, say ya get the lone geek payin' ten bucks a ticket...he or she can save that ten, and apply it to the eventual DVD release for the same reason.
And since DC's animated films are now known as direct to DVD, it'll be an even harder sell for 'em to get folks into theaters.
Marvel's animated efforts pretty much suck, so they'll stick with the live action, for sure.
And everyone else can keep doin' what they're doin' & hope for the best.