Not to mention it takes twice as long because you're unloading an entire trolley onto a space that holds maybe 4 items, you're scanning, and you're bagging. There's no area to actually work and put all your shit, this doesn't even include the 4-12 times you need the person to come fix the broken machine, but that 1 person is busy fixing 4 other people's broken machines.
Something that would take you and a professional working together 5 minutes ends up taking 10+ minutes