Just my personal benchmark.
Having done a lot of work around my house, I appreciate being able to slide the largest single object I'm likely to purchase inside my car. Also in this category: seven foot Christmas trees. Meanwhile, little Toyotas have to try and tie such things to their roofs.
On a windy day, you can see the small-car plywood haulers sailing gracefully back and forth in the sky over the high cliffs of the Pacific coast.