Several reasons for this.... for one, my steer tires on the truck are inflated to 120 psi and the drive and trailer tires at 110. Heck of a lot of pressure (then drop all that weight on top of them - about 4500 lbs per tire). But, the original reason they started using cages for truck tires was because the tire rim was 2 separate pieces that would come apart on inflation if not assembled correctly (only one piece wheels these days).

I've never blown up my bike tires...... but, maybe I should get the mech's at work to build me a cage for the bike tires.