They can be very dangerous. We had a scaper slide off the road into the ditch while running wide open and it caused the tire to blow off the rim. It tore up the fender and fender bracket which took a rosebud in order to straighten. A house about 100' away had pictures fall off the wall, the homeowners came outside to see what happened.
A lot of people don't realize but air compressor tanks will do the same if the tank is in bad shape or if a relief valve doesn't work. There are some wicked pics of a few on the internet and the tank becomes shrapnel.
Yep, anything w a two piece rim requires a cage like that by law. NASTY things can happen. More than a few guys killed and maimed airing up w no cages.