Oh, we have self-checkout counters, too. Thing is that not everybody uses them and prefers going to the cashier, and the self-checkout counters still have some cashiers to help the people out when they have problems. In other words, while there will probably be a bit less cashiers, they just won't go away.
It doesn't matter if it is a little inconvenient. If it saves the company money they will do it. They can also lower the price of their products because of automation which will actually make customers a lot happier than some cashier.