Keep cost down, most likely? Why purchase chairs when worker's can stand. Easier to replace a member of staff, than have to buy & replace a chair. Not to mention cost effective.

Not only do they have to stand for hours on end for shit pay and few breaks, if any, those "lucky to be employed" employees are fortunate to have to pack every customers bag for them, as well.

I pack my own bags, I've got arms and a capable human being. Feel like I'm a five year old when cashier's start doing it for me. Plus, I can't tolerate standing, watching. Weep :/

Oh, and if you are a cashier standing twiddling your thumbs and contemplating a one second bathroom break, because, timez are slow and nobody is at your checkout, then you have move to the busy line, pack bags, and if really lucky, you get to trundle off away to the car park, with either two bags in the shopping cart or fifty, then have the pleasure of packing those bags in trunk of the customer's car (car boot for those in the UK) I have no idea, if when those customer's get home they might wonder how bags of shopping arrived in the trunk, must have been by magic, because they sure didn't interact with any of the checkout staff working in the store, so how on earth could they have materialized all by themselves, well, they sure didn't carry them, or thank anyone for placing them the trunk? How, indeed? What a mystery.