Did you try them, or were you afraid to look silly? I think these machines do use your body weight. It won't be a challenge if you lift, but it's actual exercise. I had fun playing with similar equipment in a park in Lisbon (on top of a steep hill).

Pull-up bars would be better, and I do see people using those. There aren't any in my neighborhood, so I improvise and use football goals to do chin-ups.