I think a lot of it is that people have just picked 'their' gas station. I typically go to the same gas station over and over just because of the convenience and how close it is to me, unsure if I'd even save a few bucks by going somewhere else.
Name brands and their marketing does work on people though, rewards programs and all that keep people invested in the brand by using it.
Me personally... cheapest gas from GasBuddy + 5% CC cashback is what I usually do.
"full serve" sounds like NJ, haven't seen that nonsense anywhere else LOL
Yeah I saw this happen a few times near me as well -- only because of the massive volatility in the market which causes some to just not change their prices for a few days and be able to reap the high margin rewards of that.
GasBuddy works though, amazing app. But only when I'm outside of where I live. Not gonna chase a buck or two when I'm coming home tired from work.