Seems it was that way on the trucks 3/4 ton and larger up into the '70s and early '80s. Not sure as to why, but the tire itself was an extra cost option. The only thing I can think is that maybe they figured that the purchaser could get a tire for less than what it would cost to add it to the truck, thus keeping the cost of the truck down in order to compete with rival manufacturers.

Bill Burmeister