"most people only need a small family size car"
Even in town, I will find myself using my truck's "truck" capabilities at least 2 times a week for things which would be awkward or impossible with a "small family sized car".
* Going to the grandparents' house with the kids and their bikes
* Helping a neighbor donate furniture
* Getting soil for the garden
* Getting plants for the garden
* Camping
* Moving equipment for work
Granted, I've got a Tacoma and not an F150, and I largely agree that large trucks are excessive (and they've been made to be so due to fuel use regulations not consumer desire). But, you can't buy "small family sized car" today with the capacity and capability of a 1980s family sedan.
You used to be able to get a family sedan that's big enough to take you and your family to do things, but 'efficiency' and 'safety' mandated features and capabilities which were no longer possible in smaller vehicles - so they pushed everyone to 'commercially exempt' vehicles, instead, because those have the capability to do the things people want to do. You can track the advent of the double cab pickup to the changes in government regulations exactly.