Basically nothing else in our society works this way. Basically nothing has changeable firmware.

A whole lot of important things used to run on mechanical control systems. Someone with a modicum of mechanical talent and a box of simple hand tools could disassemble most of them and figure out how they work. Repairs were generally possible, and if original parts weren't available, there was a good chance of being able to improvise something in a home workshop or by paying a local machine shop. Modifications were also possible.

Making everything with a computer in it locked down and proprietary was a choice.