Here it's more like a forgotten law than a freedom. It's typically the farming families sending their kids (or more frequently their nieces/nephews/wards, most people here didn't give birth to their own kids) on the trucks to carry supplies. Police are probably aware but it comes up very infrequently, it's one of those "redneck toughguy maturity stereotype" things for a lack of a better way to explain. I assume public roads are involved, but that status for roads is very relative here unless you're talking about city highways. All this I learned as classmates of my school system who weren't too urban would brag all the time that "I'm years ahead of you" and stuff when people took their driver's tests.