I would be genuinely surprised if a large number of people were still using Gamestop for PC games, considering that their physical inventory is next to nothing. However they're harder to avoid for console games.
Never really understood why people feel that way. You can buy console games from the internet. If you buy from Amazon, you get free shipping and no tax. You can pay 99 cents for release day delivery. It's quick, easy and you aren't supporting a worthless company like GameStop.