[defanor]

I wouldn't count on that: many things that seem straightforward, especially to an adult tech-savvy person if those things are tech-related, are far from that for others. And even tech-savvy people can be (and often are) careless, distracted/preoccupied/unfocused, making mistakes; I think pressing a "start" button automatically upon closing the door is something that can happen easily. Also as a rule, extra guards, safety measures, and/or warnings are good, especially when irreversible damage can happen.

Edit: actually there's an example of an unexpected mistake in this thread already, in the comment by hanoz. As mentioned before, listing unplugging as the first step would be useful.