Why diesel trucks?

All I can relate to is....with my 1971 Eldorado camper, at almost 3800 lbs, I would NEVER try to pull the sierras, or go up even the San Gabriels with my horses in tow, and the camper on.....Linda and I did go thru 9 states with our load, from California, thru Nevada, up thru Utah, to Wyoming. Then across Wyoming camping with the horses, to South Dakota and Crazy Horse, then Mt Rushmore, and Custer State park, off to Yellowstone, and out to Montana, then to Idaho, and into Washington. Stayed with friends camping and riding in Washington, Montana, and when it came time to head south, into Oregon, and ride at Clear lake, then to the Redwoods, and down the coastal side of Kommifornia.
My 05 Cummins in my Ram did not miss a beat, and even got over 11 mpg coming across Wyoming, and east side of Oregon. and Home.