In the vein of Sixty Fiver's post above, it is worth remembering too that even single speed bicycles can be set up to suit local needs. I think my approach is a little bit different than his, but still even if it's just one speed, you can freely change in what you like in many cases.
In my case I run a stock single speed gearing on my ballooners, which is usually a pretty high gearing, especially in the pre WW2 Schwinn-Henderson. I do have custom chain rings for the ballooners that are a little bit lower geared than the stock stuff, but since I like originality as much as possible, I stick with the stock components where I can.
My approach is that I very much prefer stock gearing for originality if I can get away with it. If the terrain is really THAT bad, I have my 3 speeds to go to (which do in fact have 22 tooth cogs to lower the gearing a bit). So you could get the best of both worlds-- pull out the high single speed ballooner for a shorter, flatter ride. For a longer, hilly ride, pull out the customized 22 tooth 3 speed and climb a few hills. Who says you can't have both a single speed and a geared bike?
These are pretty obvious points, I think, but certainly worth mentioning.
As a bit of humor: I honestly thought until I was probably 14-15 or so that most bikes were single speeds. Most people didn't ride bikes where I lived because of the long, rural distances to travel. My bikes when I was younger were all single speeds. I got my first 3 speed in college. I started with a little Schwinn coaster bicycle from the 1980s and moved up to my dad's '62 Higgins middleweight. I got that going again when I was 10-11 and then moved up to my grandfather's '36 Schwinn-Henderson (New Departure D model coaster). I revived that one when I was in high school and then got a car. It was only in high school that I realized how many geared bikes were around because I had to run down to the shop to get replacement tires for the Henderson. I guess you know what you grow up with best of all, and for years it seemed to me as if the norm was fat tires, a single speed, and just coaster brakes. Go figure
