Could be convivence for them. I have two Sunoco stations near me. One I drive by every day. The other is not too far, but I have to go out of my way to go there, and that one is typically 5 cents less than the one closest to my house. (I have the Sunoco credit card that gets me 5 cents off the cash price) So I usually use the one closer to home, unless I'm out running errands near the other one. We also have a Costco about a 5-10 minute drive from home, depending on how many red lights I hit. There is always a line there, so even though it's the cheapest, near me, I avoid it because I'd rather just pull in, pump, and go. Not wait 10 minutes just to get to a pump.