Even with the loyalty card discount, you can usually find the same price or cheaper fuel down the street at an independent station. I like them because I know I can get my rig in and out without doing a waltz maneuvering around other vehicles and obstacles. And nice restrooms that do not look like a haz-mat site (must partially extend a slide on our rig to use the toilet). Those are worth a few cents per gallon to me.
Now, if the regular passenger cars would stop using the RV lanes, and then going to eat lunch inside while parked at the pump with me waiting behind...