Why do Americans *need* to buy a large vehicle if they have a family?

It isn't like this in most other countries. I see people in the US all the time post that they need to sell their sedan and get 7 seat SUV because they are going to have a kid.

The first car I remember my parents having with two kids was a two-door Datsun, and later, they moved up to a Toyota Camry. People in many countries will fit a family of 4 on a 49cc scooter!

If I'm to have kids, is it basically required now to have a large SUV in the US, or you're seen as socially unacceptable and unsafe - and that a car can't cut it?