Because the roads aren’t super wide, straight and empty in western PA. And the tires and brakes on this truck simply aren’t made for it. Why do you think it has the factory limit?An OEM Fox 3.0 is stiffer at different sections of travel than a strut from a half ton with 32" pizza cutters on 20s. At the top, arguably its a similar rate without progressive springs.
Why are you so afraid of triple digits in a 5500lb vehicle? If you're afraid of the energy transfer in a crash, 18 wheelers and tri-axles shouldn't be allowed on highways, yet I'm sure you've been passed by one doing 75.