[mistersys]

In these stores, cashiers are waiting around most of the time. That's the issue. They couldn't stay in business because they had to pay for the cashier to checkout as well as wait around. By letting customers checkout, there's no more wasted money spent on employees waiting around.

Also, the stores that are most promising don't require checkout at all, so that's an entire category of human effort eliminated, for better or worse.

[bluGill]

Most stores keep one person up front when they are not busy, the rest of the checkout clerks wonder the store looking for things out of place, stocking shelves, finding or customers to help. Each store has their own set of duties but for the most part there are plenty of tasks to do when people aren't waiting in line.