Many people are patreon or other subscribers. Not needed to watch ads. I would rather pay than waste my bandwidth while on train.
I wish there was a tip jar under each video and that it integrated with alternative frontends such as NewPipe, but I also don't want to hear "don't forget to like and subscribe, make sure to hit the bell, and consider leaving a tip" in every single video.
I don't know why youtube forces people do that, but it'd be nice if they fixed their algorithm so that it wasn't needed.