A few people have pointed out that explosives can explode regardless of the message; I'd like to question, if it needs a specific message to fire them, how fragile is the system that delivers the message?

Yes, in an accident the airbag generally fires so quickly that it happens before physical damage occurs to the device firing it, but needing a specific message (over CAN bus perhaps?) makes the system much more fragile. What if there's a fender bender the week or month before, and causes light damage to the system? One bit is more robust by an order of magnitude than two, and so on.