Unexpected interface outcomes per hour
It's intuitive that tools sometimes fail. You're often not surprised when they do. It's an ingrained experience in using any tool. When I swing a hammer, I expect to miss. In my mind I chalk that mostly up to myself (I know that I don't always swing the handle straight, and then head will miss by a centimeter or two).
I don't typically blame the hammer for that, even though when you think about it you definitely could. A heavy hammer for driving framing nails is a terrible tool for driving picture frame finishing nails into your drywall and if you use it, you'll probably end up with some angled nicks to the side. So right now because I don't have a nice light finishing hammer, I am extra careful and slow with the heavy hammer when putting up pictures and I even grip it higher up the handle towards the head so that I have less leverage and less acceleration.
So users know the the tool doesn't always fit the job perfectly and habitually modify their behavior to reduce their exposure to mistaken uses of the tool.
