At the end of the day, when reliability, pretense and everything else is put to bed, a single speed is just plain fun, and none more than a fixed-gear.
Herd animal this...
48-16 (78.9 inch) gearing and did 3000 ft climbing this Saturday so no, not just for flat lands.
Lots of misconception and misinformation here from those who have zero experience. More to come I'm sure.