Agreed, also i like to stack my bag very methodically with heavier and more sturdy items at the bottom, cold things together, interlock and tetris everything so the bag has its own integrity and doesnt collapse and spill items out into the car after a corner.
Yes i know the checkout person also stacks in a similar fashion but they are paid the slap it through and into a bag as fast as possible to serve the next customer and i dont mind sacrificing an extra 15seconds of my day over the bag stacking operation to do it right.

Man, where does everyone in the comments live that it still works like this? Where I'm at, they basically have attempted to replace like 90% of cashier jobs with these machines. There is often either no cashier at all, or one single cashier with like 5 people in their line, each with shopping carts filled to the brim.

The self checkout lines routinely reach lines of 10+ people with many old people who struggle using the machines forced to use them and gumming up the operations more. I avoid going to the grocery store like the plague during any kind of higher traffic time because I don't want to wait in line for 15 mins.

Other issue with self checkout machines is that some places (Kroger, looking at you) weigh the bag every time you scan an item before you can scan the next, which makes things go soooooo slow.

Not to mention that I prefer using my own bag(s) when I can, and whenever I go up to a manned checkout especially with a bagger and hand them my bag to use, at least half the time they start to panic as if they haven't seen this before, and then they're eager to start using the plastic bags after my bag is barely half full. This is even in stores that sell their own reusable checkout bags. At the self checkout, I can use my own bag worry-free and fill it however full I want, and if I overfill it, that's my problem and not on the store, so they don't have to worry either.