States don't have rights. People have rights. States have power, but that power comes from, and is limited by, the people.
Sounds trivial, but in fact, it marks a great, great, great big difference.
The concept that the state has the right or power to dictate the condition for utilization of the motorways is founded in the concept of commerce. This is legal concept dating back to the founding of the country. As for motor vehicles, it dates back to the early 20th century.
You have no Right to drive a motorcycle, car, truck, or any vehicle on state or federal highways. That is a privilege granted by the states.
Your point is a fine one, but I will grant it to you.
In fact, the state has to defer tot he federal government based on utilization of roadways when the state and federal systems overlap. Where in we have no federal laws in the area of helmets and protective gear, we do have national safety standards that have repeatedly been upheld by conservative and liberal judges alike.