This is one reason I'm kinda fond of a lot of fan media related communities. Since things like fanfiction, mods and fan games are in legally murky territory, you can't really make money off of them, especially not directly.

It's a great deterrent against grifters and optimisers, since you can't sell your work and you can't set up a company to commercialise it, so anyone uninterested in the community or series has no incentive to get involved.

Sadly, it's really hard to achieve something similar in most fields, due to the incentive to turn everything into a side hustle.