I've been asking the same thing. The mission statement introduced in JLA Rebirth isn't really jiving with the actual series. There's really no logical reason why Batman needed to create his own separate Justice League if they're not doing anything radical or different from the regular JL.
And what's worse: I don't even think the existence of this JLA has even been mentioned in any of Batman's other books. Like, no one in the Justice League has said anything about the fact that Batman just up and created his own Justice League. With Lobo!