I would like to point out that you can be a total ****er and still ride single-speed bikes, so it's not about the scene for everyone. Regardless, if you apply too much logic to bicycling, you'll either find yourself walking, for more exercise, or riding a Harley, for less. Anything in between is just because you like doing things that way.

(And I note that the original post asked about single-speed, not fixed gear.)