Exactly. I don't work at the grocery store so why should I scan and bag my own groceries? I don't.
I’m okay with bagging my own groceries (in paper bags) because of “efficiency” (denser packing than they will do) and “sorting” (these items go in the fridge, and these in the pantry...). I generally send things down the line that way anyhow (heavier items up first). The baggers I’ve seen wait until 50% of my purchase has cleared the cashier and it’s just jumbled.
One of the times I was grocery shopping after work, a clerk tried to guide me to the self service. I told her I’d been working with computers all day, I was ready to have someone else do it for me.