A lot of people who buy trucks these days just need something that can tow a travel trailer or a boat to their favorite camp site a few times a year. It's not that they need a truck on a day to day basis, but they might need the towing capability on occasion. That's why these trucks are a weird combination of luxury sedan (with their leather seats and high end interiors) and pickup truck. Most of the time they use it like a regular car, but sometimes they might need the towing capability.
Rental companies, at least in America, have policies against using their vehicles to tow things.
In addition the truck in front has to be imported to the US and there's weird regulations about purchasing them so you can only buy used. As far as I know you can't import a new model. If a car is newer than 25 years old it can not be imported unless it meets the requirements of US Office of Vehicle Safety Compliance.
I think it is regulatory. However getting US politicians to do what's right is never trivial. It would take the legislative branch to change the regulations, while likely ignoring lobbyists within the automotive industry. It's fixable but it won't be fixed.
Michigan is an important swing state, and the UAW is a major political player nationally. Ironically, that doesn't stop the US automakers from routinely screwing over auto workers and labor in general.
Part of the issue there is that for a large number of people the 'few times a year' are major holidays when everybody else wants to tow their house-sized RV and boat to the lake for a day or two. The rental fleet just isn't big enough to service the surge demand.
Your Subi wouldn't be able to pull some of these American travel trailers. Many of them are absolutely massive, they're like a luxury condo on wheels.
We have no sense of reasonable proportion here in the US. Everything must be unnecessarily large and unwieldy, gaudy and exorbitant. Bigger is always better here in the good 'ol US of A.
Can't forget the boat! For reference, while this isn't typical, it's not uncommon. That's a pretty small travel trailer and boat. I've seen this setup with much bigger trailers and boats several times.