That's not automation though. Self checkout is just making the customer do the cashiers job for free before realizing that customers suck at doing these things correctly because it's not their job.
I grew up in a grocery store, quite literally, so I have way big expertise here. The problem with self checkouts isn't that customers suck, it's that the self-checkout doesn't trust the cashier (that's you in case you missed it) and so doesn't allow the kind of actions that make checking out fast.
All self-checkouts have a separate bagging area which is a large scale or set of scales which weigh the items that you put in the bags after you scan them. This means that you have to scan a single item then bag that item, wait for the scale to notice and acknowledge the change in weight, then you can go on to the next item. Scales typically don't register small changes in weight very well, and with 50 lbs. of stuff on a scale adding a typical item changes the weight by only 1%. That might not be enough to even cause movement of the scale for it to notice the weight change. When that happens, the automated checkout complains and the human cashier who is watching all of the automated checkouts has to intervene.
A regular cashier has no such inhibitions and simply scans each item as fast as he can with an audible beep to confirm that the item has been scanned. A good cashier will have items in both hands and run them over the scanner as fast as he can and simply rescan anything that causes no beep. This system allows the regular cashier to be around 10 times as fast - possibly even faster - than the self checkout.
If people could be trusted better, self checkouts could be made far better. In their current form they're borderline unusable for more than 2 or 3 items. In our local Walmart they removed them after the first year due to rampant theft around them, so it's a real problem.
People often think it's a problem similar to an ATM. When I was a kid and I wanted to deposit or withdraw money from my bank account I actually went into the bank with my savings book and saw a teller. The ATM actually sped this process up for the most part, but what it does is far simpler than the automated checkout and the user has far less control over the transaction. Think about it - it's not like you get a big bundle of cash and then tell the ATM how much you're taking. The ATM is more akin to a vending machine.
At Harris Teeter here and now Publix they're moving to "online ordering". At Harris Teeter you order online and later come by the store and they bring your stuff to your car. In time (yes, it's coming) someone will move to a warehouse setup with robots to pick most of the orders. Expect it. Self checkouts have reached their limit but the future is automation.