Mechanical objects frequently fail unexpectedly, especially if you're trying to do something weird or unusual. We're just used to living in a world of machines that are in their second century of iterative improvement.

I make installation art, and from personal experience, despite being an equally shitty programmer as I am an engineer, the software is way more reliable, and there are way fewer ways in which it can fail. Anything from materials being not what they say they are, to some jackass accidentally making earth live, to stuff catching on fire - it's all possible.