There are also reasons, besides just enjoying superfluous moving parts, that so many don't. Bring your SS/fixed up to the Heights and show me how it can tow 100 pounds of kid trailer up a 25% grade some time.

Everybody doesn't live on the flats, everybody doesn't have quads of adamantine, and everybody doesn't need a single-speed. If you're in reasonably good shape, live in Chelsea, and don't think there's a world above 34th Street, go for it. (In fact, I think it's required.)

If you don't know where you're going to live yet, or where you're going to want to travel, it's probably not prudent to make the decision at this juncture.