I own multiple station wagons fully agree with you. But what you're missing is that it's not about the ability to do things, it's about the image projected when doing them.

Over-specing vehicles is one of the ways the well to do advertise their well-to-do-ness. It's like a marble countertop but for the roads.

Sure you can put three kids in the back row of a Sentra, it has three seatbelts there after all. Sure you can haul plywood on anything with a roof-rack, that's what it's there for. Sure you can shove a washer in a Prius. All those things work great. Bust for most of HN to do them regularly would be "behavior below one's pay-grade" so to speak.