American trucks are built for towing -- it's one of the reasons they are so big and heavy and expensive -- so I get where the "trucks are for towing" wisdom comes from.
But it's still funny to me. Because in my mind one of the main perks of an open bed is that you can do so much before having to deal with a trailer (which are super annoying, especially in cities, especially without off-street parking).
Which I guess is just to say: maybe there's a market for a truck that can't tow much, because maybe there's a portion of the market that wants an open bed but doesn't need to tow a massive camper or whatever.