I cut my first lawn as a kid with one of those. 1963. Every little twig I ran over would jam the rotating cutters. Took me two hours for just the front lawn, so the lady gave me $1.25 instead of the dollar we had agreed on.
I have a couple of reel mowers, but I don’t use them as a primary tool. We have a 10,000 sq. ft. lawn and several trees, so twigs can be a challenge, especially if it’s been windy.
They seem to make the grass look nicer, though, and I can use them at hours when a gas mower would be disruptive. I’ve cut my grass at 9:30 at night before.