My car can happily seat 4 adults (so let’s say 250kg) and weighs a touch over 1000kg, so the ratio is 0.25. 0.1 would mean that a car that seats just 4 adults weighs 2.5 tonnes, which seems extreme?
Also going off maximum human capacity isn't great in context, as the average car journey has <1.5 occupants. Not to mention if this was codified, car manufacturers would simply put folding seats in the trunk.
Fair enough, but then we could decide the relevant ratio is one human / GVW.
[0] https://www.edmunds.com/chevrolet/silverado-1500/2021/featur...
The Yukon SUV that Arnold Schwarzenegger drives weights over 2.7 metric tons (6k pounds).
The Tesla truck is announced to pass the 8,500 pounds mark, or around 3.8 metric tons (!!)