Do you hear him trying to muster some deep philosophical meaning from a film about Superman and Batman punching each other? "Power engenders fear" or some shit.
He's an Oscar winning actor/director who has some compulsion to be in a comic book film, a compulsion that even he probably doesn't understand. Maybe it's penance for Daredevil.
Or he's just a nerd but is also going through a divorce and probably not in the mood for a bunch of public appearances right now in which awkward questions could be asked?