I got a 40 gallon auxiliary fuel tank for Christmas a couple years ago. You couldn't make me give it up. I stop when I want to stop, it's not dictated by my fuel tank. I can travel all day and never have to worry about getting into and out of a filling station. Fill up at the end of the day when the trailer is dropped.
Like Old-Biscuit said, some people just don't realize that getting fuel off the interstate can be a bit problematic, not just finding some, but finding a station that you can get your 40' toyhauler into and out of.