Air breaks on on heavy trucks are a good thing. On tractor/trailer or a train think about how much fun it would be to drop a trailer if you had hydrolic breaks?
Think about going down a long steep grade and your hydrolic fluid is so hot that its boiling in the pistons and now you have air in them. No breaks!
Air breaks are easy to adjust and you have an air gage or two to tell you when may have a problem.
True if you ignore air breaks you can get into serious trouble.
Air leaks,ruptured air line or a weak compressor? Oops get ready to come to a screeching halt. I hope you know how to cage the rear breaks or fix the problem otherwise you wont be going anywhare soon. :P
Air breaks just make good sence on a big heavy truck.