There used to be a lot of stores selling used PC games in the late 90s / early 2000s. What killed it (I think) was that people would sell a used boxed PC game

There used to be a lot of stores selling used PC games in the late 90s / early 2000s. What killed it (I think) was that people would sell a used boxed PC game and then download the pirate version but re-use the legitimate CD key for multiplayer. So you would buy a used game and try to play it online but get "Your CD key is already in use" messages half the time. I got burned by this a few times. This is also one of the reasons that stores stopped accepting returns of PC games. People would buy a game , copy down the CD key and then return it for refund claiming that it didn't work.