Andreas has been making videos (https://www.youtube.com/c/AndreasKling/videos) sharing his journey: technical ones working on some part of the system, as well as more personal ones talking about his philosophy, struggles and moments of joy.

I'm just one of many but I'm guessing his sincerity combined with his technical abilities make it all very compelling to watch and contribute with money or code, even though the system isn't at a point where you would want to use it.

Basically: it's a fun, open, ambitious project whose story is being told mainly through videos, with a kind and interesting person behind it.

Personally I want to encourage a very talented developers continued development of his ambitious SerenityOS vision whose journey is thoroughly documented in his YouTube channel which is an amazing treasure resource for learning how different parts of the OS/Kernel/GUI/Browser/JS VM/x86 Emulator/etc are implemented.

At first I never expected SerenityOS would ever be advanced enough to use, but seeing how much it has progressed and the active community that's garnered around it has made me a believer.

Up until now he's been developing as a side project, I'm excited to see where he can take it working on it full-time.

Probably not much practical use, but that's not really the point. Some may learn from it, some will draw inspiration from it, some just want to support the author and some probably just think the world is a better place with projects like this in it. Think of it as the technical version of supporting the arts.