Often when people start driving a much bigger vehicle than they are used to they get this picture in their head of how huge it is...this is easy to do. We have all walked up from far away on our vehicles and marveled at how long and big it is.
But the reality is...it's really not that big by comparison to most commercial vehicles. And larger commercial vehicles are found in these gas stations all the time, for delivery, to get a snack or coffee and often times to get fuel. Some of them are far less maneuverable than your rig.
Also many of us tend to carry that idea of "bigness" in their head when driving. Your Pickup truck with a 40 foot trailer can and will fit in many more places than you may think.
The key are the pivot points and the distance between them. The pivot point of the trailer connection to the truck and the pivot point at the trailer or Coach axles. You might be surprised at how closely those trailer axles follow the track of your rear truck wheels. This is called Off Tracking.
Really experienced drivers know how to "set up" for any given turn or entrance to pumps. Almost anyone can learn to do it but you have to try it a few times.
My guess is that most RVer's are filling up in regular stations (as opposed to Truck Stops) which should be telling those that feel they cant do it that it can and is being done daily by thousands and thousands all over the country.
I find the smaller stations including those smaller Murphy ones to be easier and quicker and much much less hassle overall than a Flying J/Pilot or most other Truck stops.