Even that didn't work well, when I was at an airport recently I had investigated 4-5 items as I had some time to kill. When I was walking out it wanted to bill me for 70 dollars even though I only had a bottle of water and a candy bar.

I have little trust that a corporate behemoth will do right by me and refund the discrepancy at an unspecified later time as it says it will on checkout.

This keeps me away from these sorts of stores if I can avoid them, which is pretty much always (so far, anyway). I would be absolutely shocked if the error rate was comparable to a normal checkout process and I don't want to waste the cognitive overhead of either wondering how much I'm getting ripped off by a corporation or having to go back and review and try to resolve overcharges.

They pay the most for human involvement. Wages, special conditions, and insurance are exponentially higher than their plans of warehouse to end-user via lockers and drones.