It really does suck that companies are cracking down so hard on Trainers. I think that the companies should be fine with it as long as we are still only making them work for Singleplayer.
I think it is because of achievements. I noticed cheat codes stopped being in games around the same time achievements started to pop up. I like how RockStar handled it with GTA IV. People can still use cheats, it would just block achievements. Same way with New Vegas on Steam. People can use console commands but it would block achievements. I don't understand why more game developers don't do that.