@Alguecool The rules of this site are in place to protect the site from copyright holders' claims, and are based on the wishes of Kunos. Whether or not the rules are justified, logical, or consistent isn't really relevant, unfortunately. Kunos owns the content of their game, and are free to dictate how that content is used. RaceDepartment's staff has decided to enforce the rules laid out by Kunos for their own protection.
As for some 'illegal' content being hosted here; admins aren't going to trawl through every single thing to find a breach. They'll only investigate something if there's cause, like a report, so many things wind up staying in place because they haven't been reported or the staff is too busy to investigate at a particular time. RD's policy is that any game rip is not allowed here, so your comment about rips being allowed is unfounded. What goes on in other communities isn't relevant to RD's rules.
You don't have to like, or understand, it, but that is what the situation is. If you do not wish to abide by the rules in place, there are plenty of other places that choose not to abide by those rules.
FWIW I'd tend to agree that reusing game assets for mods of that game should be fair territory, but that is not the stance of the party that actually owns the content. There is a large misconception amongst most people when it comes to games/software: you didn't buy the game or the content, you buy a license to use the game and its content. That is how nearly all games and software work, that's why they nearly all contain some form of EULA. This isn't a digital delivery issue, either, it was true for physical media based software, too. Again, we don't have to like that, but it is how it is.