Do you not do the same with a cashier?
(This is getting tangential, but I do exactly what you describe, and I really appreciate that I can do it on my terms, without having to accommodate three other people: the one in front of me, the cashier, and the one next in line.)
Ah, I see. I don't live in the US, so I never experienced that. In Hungary, there is zero service, the cashier sits behind a counter, the shopper unloads everything to a conveyor, cashier beeps every item, shopper puts them back into their cart. For heavy items, the cashier comes out with a portable beeper, and does the job with that. And now with self-service, it's on the shopper to do the exact same.
I was thinking of Costco, where loads are big and they do a good part of it for you, except for the smaller stuff.