Exactly. The difference in road wear from a full-sized pickup truck and a Prius is inconsequential. In fact, the owner of the full-sized pickup truck pays far more (on a per-mile basis) in road taxes than any other vehicle class relative to the impact on road wear than any other user. That’s because a truck that gets 18 mpg will use twice as much fuel as a car that gets 36 mpg, but doesn’t cause anywhere close to twice the wear and tear on the system.
Most states also charge more in their registration to trucks.
Even horse trailers get charged by weight.