Re: Someone please explain why....
Not all citizens fought alongside Batman. It was only the GCPD.
And while I still understand your point, there will still need to be someone that would have to fight outside the lines of the law since there is a likely chance for there to be crime again with the Dent Act demolished...mobs could start to show up once more. Blake being that person is still very, very likely to resume duties that Bruce Wayne had.