Until the 80's or so it was common place to see kids, little kids, riding in the back of pickup trucks too so that would not be far fetched. Don't know that i would want to be sitting on top that gas tank if you get rear ended!
No doubt, it's just not as common place as it was earlier on. When we went to town in the truck, we were in the back, if the weather was bad we went in moms car.I did it in the late 90s and early 00s as a kid.