As a machinist who occasionally write programs in G-Code from scratch and adjusts them almost daily I can say even if it doesn't kill anyone, it might send 25 pounds of brass spinning at 750 RPM flying across the shop. People take writing harmless software for granted, but there are many fields where a software failure can cause a serious emergency. There are embedded systems lurking in a huge variety of machines which operate with deadly forces... from aircraft to power plants to industrial processes to the car you drive to work.