My dad used a reel mower when we lived on base housing. The yard was very small.
The advantage is no fuel is required and it’s always ready to work.
A reel mower will eventually get dull. But a file will sharpen them. You wouldn’t cut tall grass with a reel mower. That wasn’t a problem on base. Regulations required regular mowing.
My parents eventually bought a house with a big yard. They bought a power mower from Sears.
I have a reel mower. Yeah, you can cut taller grass with one, but you’re going to have to mow it more than once. I still use it pretty often if I haven’t missed a week or two of mowing. On the plus side there is no deck to get clogged up with grass, so it mows a wet lawn just fine (heck, I’ve mowed in the rain using mine). Also, it’s about as simple to work on and repair as a kid’s bike. My yard is about 3/4 an acre, so it’s good exercise.