Because repairs can be made with air in the tire and the tire on the vehicle.
Small enough to stow right in with your gear, equipment or in your trunk.
The average size repair costs about a dollar.
PSP material is designed to last the life of the tire and the tire can be recapped.
Tested by the leading tire manufacturers and the U.S. Department of Defense under extreme conditions, it has proved effective and exceeds all D.O.T. standards.