It is kinda like the 'law' that you needed to have someone with a red lantern in front of your car at night in New York in 1903. The 'law' might still be on the books, but in reality, the trucks have changed so much that the law is not really required to make the truck safe.
While back in 1973, a truck with heavy duty front springs and a plow mounted on it might not be safe for also carrying a camper at the same time, todays trucks are a long ways from the 1973 truck. Much as the model T truck is different from a 1954 truck, and the 1973 truck.
Fred.