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.
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.