For families with 3 children, the child car seat requirement generally pushes them into a minivan because you can't install car seats 3 to a row, so you need an extra row. And then you still max out at 1 friend instead of 3, because even a minivan won't seat more than 4 child car seats.
It's also not magic getting your children into a car seat. It takes time, the angles are awkward, and when parked on a busy road it often exposes parents to traffic. I've only heard of 1 fatal accident through where a parent was struck by a car (sideswiped) while fiddling with a car seat.