The same reason non-autonomous ones are so big. It's a status symbol, plus there's the arms race of "bigger truck wins in an accident"

> bigger truck wins in an accident

And that's why I go by tram. :)

Jokes aside, it seems foolish to create an entirely new class of vehicle that drives itself while completely ignoring the physics of big bits of metal.

Even the original DARPA Grand Challenge in 2005 was won by a system installed on VW Taureg, an enormous two-tonne SUV.

They used a big SUV to get rough road capability, necessary for the Grand Challenge, and to have the space to rack all the equipment they needed. 13 years later, an Nvidia Jetson (a single board computer) has more computing power than their whole setup, and a medium drone can carry it.

What does autonomy have to do with it? Most regular cars would be better off as single-person vehicles; there are a few small-scale efforts in this direction (the Smart car, the G-Whiz electric car, I think BMW has an enclosed-canopy motorbike) but they largely haven't caught on.

BMW built the C1 from 2000-2002. They showed an electric version, the C1-E as a concept in 2009.

As autonomy is implemented and refined, and safety improves dramatically, new regulatory and economic models will emerge. This will spark design innovation. No doubt both single rider and shuttle-bus options will emerge, with much lighter builds as crashes decrease.

It's a test-vehicle, not the end-product.

Because A) Crash-safety and B) Luxury still being in the bigger packages.