At least most of the nay Sayers stayed off this thread.
If a person is more interested in other things in life than finding the very next fuel stop available, or, gosh, is somehow trying to make some time and not interested in visiting every other loves or flying J on I 80 then aux fuel tanks make sense.
I've packed slip tanks in my work trucks (gassers) for years. Had opportunity to toss one in my personal truck for a X country trip last year......was great.
Only stopped once for fuel between WA and WI. I had to get out and pump my fuel into the truck, but way more convienent than stopping 5x for fuel in 2 days.