Why is it we live in a world where someone creating something they release for free, for fun, for other people to freely enjoy, based on a character or idea tha

Why is it we live in a world where someone creating something they release for free, for fun, for other people to freely enjoy, based on a character or idea that some corporation owns is against the law? A large fan project existing is arguably a net positive for everyone. It's not like these projects take sales from the company, in some cases like the am2r guy or the sega fan game people, it leads legitimate careers in the game industry, it's free exposure that keeps people interested in a brand or characters. I've seen a lot of big ip based fan projects come and go over the years, i've yet to see one that would have seriously damaged the owner's business or ip in any significant way. To be honest though, i've personally refused to purchase things specifically because of dick move ip enforcements. I refuse to ever play metroid returns because of what nintendo did to the am2r guy and that is a game I would have bought. I would have bought a ds just to buy that game, was planning on it.