Childhood nostalgia? They are indeed terrible brakes from a riding perspective. But a) no cables or pads to mess up, b) beginner friendly and c) skidding. Great for kids riding around the neighborhood, the only real purpose.
It's also great for getting on tall bikes at a standstill, since you can lock the pedal and use it to step up, you do need to quickly start cycling though.
I'd love a disc up front, but as far as I know, the fork on a circa-1989 bike isn’t compatible with a front disc brake setup, making the upgrade challenging without welding.
They like it when the bike doesn't suddenly stop when they accidentally pedal a little backwards, something that happened particularly frequently when they were beginners.
They also like being able to prepare for the stop by taking their feet off the pedals and hovering them over the ground while they brake.