Games are often hard to modify and cheat in for a few reasons, be it custom file formats or that the game developers do not want you to. Quite often, they go to such lengths as to implement systems that prevent the game from being modified.
I believe that modding and cheating in games should be a personal choice; if you can squeeze even more fun out of a game, why should you let someone else decide whether you're allowed to do it or not?
Game developers: Please continue protecting online gaming experience, but please understand that we mean no harm when we want to squeeze more fun out of your loved games offline! :)