As an introvert, the unexpected upside of the self service at a supermarket is that I can - if I'm lucky - avoid people altogether. Especially first thing in the morning.
I think the bubbly, eternally helpful staff members might miss that point. Although I'm sure they get it brought to them quickly enough.
Yes, the screen has jammed and needs you to put your key in. That's the machine seeking interaction with you, not me.
It was on one such interaction this morning where I saw the unexpected upside of self service just as I had lost it - sweet solitude.