There's another factor involved.
In very busy, high traffic areas, convenience stores/gas stations, sometimes even fast food restaurants of the same brand may be positioned on opposite sides of the street (usually opposing corners of busy intersections) in order to capture traffic traveling in any direction.
Numerous studies have shown that many motorists will not bother making a left turn to go to a particular brand (even if they're loyal to that brand) and then have to make another left turn to resume their route, but if it's on their side of the street, they don't mind two right turns to stop and spend some money. By having stores on opposite corners the retailer can hope to capture a bigger percentage of the consumers traveling any direction at that intersection.
It gets real interesting in some locations where you have Circle Ks on the NE corner and the SW corner and AM/PMs on the NW corner and the SE corner! Talk about dueling banjos!!