Honestly, this is not really commonplace, at least not on the PC platform (no idea about console). There is only a handful of games I seen that sold cheatey DLC's (and with cheatey, I'm thinking of godmode esque cheats). Where does the idea that it's common came from, rose tinted nostalgia glasses?
Cheat codes are a bit less common sure, at least game specfic ones. Some games still got a dev console you can use, but it's usually engine rather than game-specfic cheats.