Why Singlespeed?

I'm not sure I can really tell you what it is about one gear, maybe the lack of drivetrain problems, the reduced bike weight, or maybe it's just the way non singlespeeders seem to think I'm hard core.

First of all, not hardcore. Singlespeed is not harder than riding a geared bike, just different. I'm faster on the hills(so long as I can stay on my bike), slower on the flats, and the downhills are just the same. The biggest difference though is the way I use the rest of my body when I ride, technical climbs take a lot more body english than I had ever used in my pre singlespeed days. I'm constantly working the bike underneath me, rocking those wide downhill bars from side to side and shifting my body fore and aft to get that extra little push when the going gets steep. At the end of a long ride with a fair number climbs I find that my arms are just as tired as my legs. It makes for a nice workout.

Lack of drivetrain weight can't be it, bike plus rider plus gear comes to something near 285 pounds, how much difference could a couple of pounds of bike make.

I think it's gotta be about the fact that I never have to work on the drivetrain, ever. No ghost shifting, no cable stretch, no dropped chains, just sweet, simple, straight forward, one speed drivetrain efficiency. A little lube every other ride to keep things quiet and I'm good to go.