Big rigs usually have huge tanks; so they can decide when and where to buy fuel.
The mileage taxes paid by truckers are entirely about states wanting drivers to pay for the roads they use as big trucks take a huge toll on local roads.
Having cars do the same thing might actually create a road system which is more responsive to actual use.
BTW, I would not mind seeing insurance combined with a mileage tax. Imagine a system where the taxes increased depending on the risks associated with a given road. This would encourage safer driving and encourage states to build better roads.