At most stores I go to - like, Lowe's, Harris Teeter, Walmart and especially Target - there are REALLY LONG lines for self-checkout. Last time I was at Target, it looked like Black Friday - all the way past all of the registers, well into the cosmetics area. Maybe 30 people. WAITING for self-checkout And I think TWO regular checkouts. Honest to God, it was so bad, I kept asking if there was some kind of special going on. Nope. I just hadn't shopped there in a while.
Line at Lowe's typically runs down one aisle; ditto Harris Teeter. There's usually a line at Walmart, about a half dozen, easy. And because it's a big store, people USUALLY have near full carts. You don't go into a giant store for groceries and just buy a bag of nuts.
BJ's is mostly self-checkout, and unless you go during off hours, they WILL queue you up down one of their long main aisles. I've seen it go all the way back to the refrigerated area. Last few times I've gone, they had NO cashiers. And it takes forever. Plus, they and Walmart appear to be taking the "checking receipt" person more seriously, so there's a line to LEAVE.