That was decided for GameStop when Valve introduced Steam. Before Steam was a download store for PC games, it was the Internet activation method for Half-Life 2. Once more PC game publishers adopted Internet activation, GameStop could no longer accept used PC games.
You mean instead of leveraging their position with Valve, they decided to throw the baby out with the bathwater. And in turn, other companies filled the niche that gamestop left behind. Now those places that sell hardware and software are successful in doing so, while they're looking at the complete collapse of their business.