Why do people make fangames?

[Jacket]

I don't know about the legality of doing something like this, but I'm pretty sure the companies don't really mind.

Tell that to Square Enix. They have a history of cease and desist orders.

Or how about Take 2 and Rockstar, who if you so much as stream playing the game enact the DCMA, despite the EULA having NOTHING to say about it.

Most companies do not enjoy this. It's the same as using Mickey Mouse to sell YOUR product.