That's because there are plenty of people who don't care about copyright, or who work around it by creating a likeness of something, without using the original asset. To expand on my earlier post, there's nothing to stop you importing assets into your game yourself if you know how, but the moment you attempt to distribute it to others is when you risk your mod being taken down and having your account temporarily barred, or even being banned completely. Nexus are strict on this because they have to be, otherwise they'd be seen to condone it, and you'd have people importing stuff left and right, which would put the entire site at risk for allowing copyright violations. Read the Nexus TOS to understand it better. by copyright standards i dont understand how that is a thing. this is the point of mods. you dont distribute them by charging a fee.