An industrial control system that crashes when it receives an unexpected network request isn't built for someone that knows exactly what they are doing. It was built by someone who wanted to expend the minimum effort possible and make contingency-handling someone else's problem.

This isn't just about hacking. A device that crashes hard when it receives a POST with an empty body may do the same thing if there's a physical glitch with its connection, or if a cosmic ray flips a bit somewhere. Devices that control industrial machinery should be more reliable than that.

If this were a hobbyist project, or a toy, that would be one thing, but these are specialized devices that cost a lot of money. They're fragile liabilities that don't belong anywhere near a shared network.