The Reason Why Are Trucks Getting Bigger

Vehicle tax in much of Switzerland is decided by the Gross Vehicle Weight (GVW). Important distinction of GVW is that it takes into account the maximum permissible operating weight, if the vehicle is fully loaded.

Drive a heavier car, pay more tax. Funnily enough, you don't see a lot of pickup trucks or minivans.

You make it sound like way simpler than it is in reality.

Tax criteria by canton:

Displacement only: AG, FR, GL, GR, LU, NW, OW, SH, SO, TG, VS, ZG

Gross weight only: AI, AR, BE, BL, JU, SG, UR

Horsepower and gross weight: SZ, TI, VD

Displacement and gross weight: ZH

Net weight and CO2 emissions: BS

Horsepower only: GE

CO2 emissions only: NE

And for the full picture you still need to add the discounts or exemptions for low and zero emission vehicles that also vary wildly.