I'm coming from the perspective of an owner of Truck and Trailer.
I make sure that the truck and trailer are all ready to go before the trip - all maintenance done, fluids, tires checked and replaced as necessary, brakes, etc. I then fill up the truck.
The rest of the trip the passengers pay for fuel. Some time I have some fuel left when we get home (of original take I purchased), sometime I don't have much.
Our trips are ~2K RT. Last year the cost was about $650 for fuel. This year was ~$500 (not including my first tank). Divide by 3 or 4 is only $40-60 difference per person.
I'm guessing most on here don't own the truck/trailer. There is a huge amount of maintenance that goes into keeping them going. I'd gladly pay 40-60 more per trip for someone else to incur the wear and tear, but no one else has a rig.
It is also better than hoping I get a few bucks at the end of the trip to clean interior and was exteriors. There is never money left at the end of a trip
Oh yeah...also - "my truck/trailer, my rules". I load sleds, etc.
It works well for us. I've only had one complaint and that was from a guy who had a truck and trailer. He chooses to split between everyone vs 3 (good for him). Saying we'll all take turns. This can work if all the same crew and all have rigs. Funny how I've not seen him/ridden with him for 3 years x 6 trips.