Not all supermarkets have retired them. In the Northeast, Stop & Shop still has use-as-you-go barcode wands, but not in all of their stores—just the ones in more upscale neighborhoods that are less likely to have shoplifting problems.
Scan-as-you-go, combined with reusable shopping bags, can be a wonderful experience, especially with a good, purpose-built scanner, and if the store is good about maintaining their produce scales with barcode printers.
The experience at Stop & Shop's big local competitor, Big Y, isn't nearly as good. Big Y uses a phone app instead of a bespoke scanner. The app eats your phone's battery like mad. It insists on making an ear-piercing beep every time you scan, with no ability to control the volume. And the "checkout" button is placed where you trigger it constantly by accident, while trying to hold the phone. On the other hand, Big Y's app lets you scan a QR code on your way out the door and pay via Apple Pay, rather than having to check out at a register (manned or self-service), which is nice.
As a whole, Big Y tried to do it cheap. Initially, they had one produce scale for scan-as-you-go; it was a modified deli scale and it displayed a QR code for you to scan—no printer to put a label on your produce for later reference (or for use at the self-checkout). They've since installed the same Bizerba printing scale that Stop & Shop uses... but with the printer disabled for some bizarre reason.