I've noticed a similar thing happening with prepared food. If there are Wawa stores in an area, there usually aren't as many sandwich or salad places nearby as you'd expect. Where I work, your options are basically Wawa or bottom-tier fast-food chains (McDonald's, Taco Bell, etc.). I really wish there were more health-oriented quick-service options (even a Chipotle would be nice), but I don't think they can compete against a place like Wawa since it's good enough for the vast majority of people.
For people scratching their heads wondering what the heck Wawa is, I have no idea what the West Coast equivalent would be. Sheetz is another similar chain on the East Coast, if that rings any bells...