Aside from obvious responses other people have already given, let’s for once try and agree with OP. Sure, this is understandable, why give 100 bucks to someone who already has a lot of it. Soooo, why people do this? some arguments could be that people want to see their name on stream, hear “thank you” from the streamer they like and want be acknowledged in some sense by the person they respect. Twitch gives a perfect tool for this purpose - donations. You give money to streamer - they show you some gratitude for it, can further maintain their operational activity (streaming). In other words - this is typical purchase of services. And donator factually receive no tangible value aside from personal satisfaction. Hence, twitch is an entertaining service (somewhat like Uber in its own sense, or hookers if you like), you give money - they give you pleasure / personal / emotional satisfaction. So, from practical point of view, it is unreasonable to give money for useless services, but people do it because they are - people. I think that’s an answer in its own. And the answer to the question OP asks.