It's a lot more complicated than you would imagine. My father in law owned a farm/home fuel distributorship for over forty years and watched most of his competition go out of business due to depending on suppliers, allotments and so on. In the 70's he bought his own transports and hired drivers in addition to driving one himself all over the country to keep his customers in fuel. It cost him a boatload of money and an audit resulted in fines as in some cases he lost money.
He retired quite a few years ago and regulations are lots worse than ever, no one can put in the hours he and his drivers did without problems from DOT, rigs are outrageous and some of the large distribution points have closed. Two river terminals closed with only one locally and the next 125 miles away.
I'm not saying someone isn't making some money, but it's probably not your local supplier.