Well, to be fair, can you blame them? Handsome billionaire playboy by day, heroic caped crusader by night. I'd be more shocked if they weren't attracted to Bruce!
Let's not forget that superheroes are often meant to be fantasies, based on our ideas of a perfect human. It makes sense that all the heroes would be constantly falling for each other, considering they were designed for us to fall for!
BTW Bruce/Babs is beyond messed up. *cringe*