I lived and biked in NYC for 10 years. I'm certainly no daredevil and not really into blowing through busy intersections and red lights. But in a city like that you need to ride somewhat aggressively and offensively because there's a lot of **** going on and people don't care about you. Admittedly the urban fixie riding is somewhat extreme and pretty much a sport but I don't think it came about just because people like to be *******s. I'm guessing it was a natural progression of the way messengers et al need to ride to survive in the city.