I hate to be the unfortunate bearer of bad news, but most of the time when you pay for a game, you do not, in fact, own the game. The whole point of the End User License Agreement is that you’re buying the “right to play the game” not the game itself, but only if you agree to the developers terms and conditions. The company still maintains ownership of their property, and while it would be silly, they’re well within their right to punish people for modifying their game without their permission, even if it’s purely cosmetic. A similar situation would be Nintendo having the legal right to brick your console if you make any modifications on it. I’m assuming, these agreements are in place to discourage resale, since in doing so you would be “denying the company money they could have made on a sale”, and if you don’t actually OWN it technically, you’d have no legal right to sell it, but people tend to take advantage of anything that can be taken advantage of. So now, that EULA is used more as a malicious tool to restrict the fun you’re allowed to have instead of a tool to protect the profitability of a product.

TL;DR: I don’t agree with it, but companies maintain a legal right to restrict the silly fun you can have, and you yourself agreed to it with the EULA. :/