A truck has to have a nose that looks like a big slab of concrete to oncoming traffic. If it doesn't men will be forced to wear dresses, sing show tunes while sitting to pee. Thems the rules.
Clearly you've never had a half-asleep sit-down pee session where your little fireman played "find the crack" with your pee stream and the toilet seat. Nothing like sleepily pulling up your pants to find your underwear cold and wet.