How exactly does the inflatable boot work to correct a broken bone?

I broke the cuboid bone of my left foot in three parts while surfing. I sled off the board and landed into the sand hitting my left foot with great impact and velocity. My bad luck. My Orthopedist let me choose between a cast and an inflatable boot. I can manage the discomfort and the pain in the *** fact that I have to keep my feet up all the time,, what bothers me is that I just do not see how the air pressure helps the healing of the bones, it almost feels like you just need to leave the bones alone and let them heal on their own.Why put the air pressure on the bones? I asked my Doctor and he says to avoid moving it too much, but to deflate the boot as needed (to scratch,clean,etc.,) in inflating and deflating the boot, am I not pushing the bones in and out? They'd be better left alone!. Am I missing something? I almost want to kick off the darn thing for good and let the bone heal by itself. What do you think? I am angry at the boot.