If you really give it some thought; Batman is an enforcer for a family business. Bruce Wayne is a capitalist. He is a person that is money-motivated. A dude of wealth and taste too. All he is doing is protecting his business Wayne Enterprise. Gotham City is where the headquarters of his businesses are at. So if the crimes take over the city they will take over his power and wealth. So he got to fight them off because nobody can do it for him other than him. The Gotham City Police already caught up fighting little crimes to be protecting a rich man’s business. Boom, here comes Batman. A mysterious figure that nobody knows is tied to Wayne Enterprises. Then he got competition with other people like Lex Crop. So why not become friends with Superman. Bruce Wayne is smart.