As in most things, "Follow the money". Dealers love selling a hundred dollars worth of iron for six hundred dollars at the closing. There is a time and place for WD hitches. I own and use one when required. I have owned several. Their popularity was promoted and needed more when we towed with sedans and station wagons. Ever see Grandpa's 58 Buick hitched to his Airstream with the back end six inches lower than the front? Modern pickups with payloads of 2,000-4,000 pounds are entirely different animals. But the myths linger on.