I flat out refuse to use the self-check-out. I don’t work there, and I don’t volunteer in a for-profit establishment. If there was a discount for using those lanes, I likely would do so, but they’re not getting my labor for nothing.
The same goes for “buying” a bag for my groceries: if they ask me to pay for a bag, I will walk out without buying anything, leaving my purchase on the belt. Even if I have had a custom sandwich made. I will not play those games.
I like the way you think! I feel exactly the same.