I use staffed checkouts for a different reason -- it is vastly faster if you are purchasing more than a few items.

All I have to do in a staffed checkout is remove items from my cart and place them on the belt. The cashier scans them, and can begin this task while I'm still emptying the cart. And most of the time, the cashier is practiced at this task and can do it quickly. When I'm in a self-checkout I see seconds wasted per item as people turn them over and around one-by-one to find where the bar code is.

And the staffed checkout usually has another person to bag the items, and again can begin doing this while the cashier scans more items, collects payment, etc.

At a self-checkout I'm doing all these tasks myself, stepwise because the computer insists that I bag each item before I scan the next one.

I always choose a cashier because they are, without fail, more efficient at getting me checked out than having me fumble with a checkout machine. And that's without having any sort of fresh produce. If I have fresh produce then the machine is even worse. Making me do the job you once paid someone to do? No thank you, grocery/bigbox store. Maybe once in the last 10 years when I had a single item and it was holiday season -- even there express checkout is usually faster.