**Except IIRC we never find out WHY. Batman giving up is his choice (presumably after Jason's fate, and even that was left vague in DKR) and Superman went "politically hamstrung". Where were all the OTHER heroes in this? Wonder Woman, the Titans, the JSA and the like? **
The government outlawed them.
**I'm a Batman fan, I'm a BIG Batman fan, he's one man in one city, that works, but to suggest that he's the ONLY man, in ANY city, is just not impressive storytelling.**
I interpret that whole entire scene. Before Supes stopped the nuke, the most dangerous city in fictional reagan era US was Gotham. When the crap hit the fan, the most dangerous city in the DC US became the safest city. Not because law and order was being enforced, or that the "system worked" or that good people decided to help one another. Rather, it was because Batman was bringing the city under his control and his rules, not the rules of the decaying, corrupt America. And the nation looked to Gotham as an example to lead them out of the crisis. It works because this is no ordinary man. No one else in America, at the time, could do what he can do. Because he is Batman.