A camper requires a special heavy duty truck and lots of add ons and provides the least amount of space and weight capacity for ones dollar. Unless people want the gain in mobility or have need for the truck as a work vehicle when the camper is not loaded in the bed a conventional travel trailer is a more economical choice. For towing a boat a motorhome provides more space, no need to crawl up to get into bed, greater load capacity, and more comfort.
Compare the cost of a 1-ton pickup for hauling the camper to the cost of a 1/2 ton pickup to tow a trailer, and not just the initial purchase price but also the cost for tires and fuel, and every aspect of using a camper involves greater cost for the owner.
I was traveling the past couple weeks and counted 49 5th wheel trailers, 64 conventional trailers, and 4 truck campers on the highway. I did not count motorhomes but there were definitely more than 4, though trailers were out in far greater numbers.