I also used to throw my mountain bike on the back of my sports car! It was, in retrospect, ridiculous.

I’ve also seen a motorcyclist having a bike mounted on a hitch!

Optimization for tiny isn’t a factor in the big outdoors. Indeed, I see more people in Sprinter vans than Teslas by mountain biking hot spots. So it’s not about “could you”, it’s about comfort and practicality of anything / everything else you may want to do beyond just lugging a bike to a trail. Such as: the optionality to go truly off road - in the vehicle not on the bike.