People don't "need" it in the sense that they need food or water but they "need" it to conform to social norms. It's a class/status thing.
How hard you work your vehicles is inversely correlated with income (generally speaking, exceptions are in abundance when you speak in generalizations like this).
If you hang out with the HN type crowd then you'll rarely if ever see someone fill every seat in a car or use a pickup to its full capacity. We're generally rich enough to afford more vehicle than we "need" in every regard (pickup trucks to haul light loads, three rows of seating for families with <4 kids, high performance German driving machines for a commute that's mostly sitting in traffic, etc, etc). At the other end of the economic spectrum people shoehorn whatever vehicle is available to them into every role it needs to fill.
Every time I'm strapping material to the roof of one of my beater cars at home depot I'm immediately self aware that I am not acting the way people of my income level are expected to by other people of the same income level. Depending your income level pressing a less than ideal vehicle into service to fit all your needs is just not an option you let yourself seriously consider.
So yeah, the people driving newish vehicles are mostly rich enough to not "need" all the capability they have and it's generally not socially acceptable for these people to go all out using their vehicles.
Edit:
You can see this playing out in the comments.
Someone says they "need" a pickup to do something and gets responses like
"No you don't, people in India haul lumber on motorcycles"
or
"But people in France can tow their their boat with a subcompact car"
While that might be true the social norms of the US do not permit middle class and upper middle class people to use the piss out of their vehicles.