In Australia you have to pay registration per vehicle even though you can only drive one at a time. This means people will buy a big vehicle that they might need occasionally instead of having a big one and a small one.
This logic is usually beat out by the existence of rental services. Is a couple hundred bucks a year to rent a truck when you need it really more expensive in the long run than owning and fueling $50,000+ truck year round?
No. I just mean that it would make more sense to pay a fee to drive any car rather than rego for each. That way you could have a small car for around town and a bigger car for when you need to go further afield without having to pay two lots of registration fees.