I have no need for a pickup, so I'm better served by a 25 foot RV than an 18 foot truck plus a 25 foot fifth wheel. Plus I'd have to find parking for 2 vehicles that don't fit in my garage, while with the RV I need just one space.
It's debatable whether the truck+trailer is easier to manage than the RV + small car. Though since we tend to take the RV to state parks and such where we don't need to drive after we park, we rarely take the car.
Everyone has different needs, but having owned pretty much every type of RV available, I'd say a truck with a fifth-wheel is much easier to mange than a coach with a flat-tow car.
A fifth-wheel is easy to backup when needed. A coach with a flat-tow car attached can't back up at all.
And as long as you have enough truck for the size fifth-wheel you have they tow much better in wind and handle curvy roads well.
While it's true that you can't back up with a towed vehicle, the advantage of the RV is that you don't have to -- only takes a few minutes to pull the pins and free the car and generally when I'm towing the car, I want to use it, so I'm going to unhook it anyway when I park, may as well unhook it before I back in the space (especially since I typically want to back in all the way and put the car in front)
But as you say, different use cases for different people - if you already have or want a truck (or other tow vehicle), a towed RV makes a lot more sense. But I don't want a daily driver that's large enough to be a tow vehicle and it makes no sense to buy a tow vehicle that's only used for towing.
It's debatable whether the truck+trailer is easier to manage than the RV + small car. Though since we tend to take the RV to state parks and such where we don't need to drive after we park, we rarely take the car.