I'm not sure the effect of this is so obvious. Clearly full-serve will have higher costs and lower margins - but then again, since it's all the same price customers might prefer full-serve and go to those stations that offer it. Will full-service have lower margins but make it up in volume? Or be some kind of loss-leader for selling snacks at the store?
I don't know - it just seems really strange? Like why not just allow them to charge more for full-service? What's the downside to the public of allowing this to just be another option?
We have both options in CA, and while full-service is somewhat rare, in most areas you can find it if you want it and are willing to pay more for it.