Only ~40% of American households have children under 18. Families are not the norm.
Exclude people who never have multiple kids, and those you have yet to have kids or whose kids have left home and large vehicles simply don’t fit most people’s lifestyles.
Which is why pickup trucks can be so popular cars just don’t have many passengers on average.
Where I live they mostly drive enormous, 4-door "pickup trucks" which can seat 5 grown adults very comfortably. While it's not quite a 7-passenger full-sized SUV, I just want to make sure you're picturing the most popular size and shape of truck when you think about pickups :D
The breakdown is somewhat vague but Regular, Extended, Crew, Quad are noticeably different cab sizes.
At the other end 3rd row pickups are coming…
Something like a $65,000 truck. LOL