I assume most cats don't travel in cars with their owners very often.
But many cats see their owners going off in their cars quite frequently.
They often hang around by the drive, watching us get in our cars and leave.
So where do cats think their humans go, when they go off in their cars?
Cats understand a bit about consistency, about the need for reproducibility in the scientific method.
So I reckon I know where cats believe we go, based on their own observations and experience, and the concept that the world is rational and predictable.
They think we go to the vet's.