You thought that was an answer?
Space is a corporate benefit, it's not a customer benefit.
Speed of check out is dependent on the customer or the customers ahead of you. They don't speed up the check out process.
They are money savers for corporations by allowing them to hire less employees, self check-outs are of zero benefit to consumers unless, as I said, you are the socially-awkward type person that doesn't like to have any interactions with humans.
Job killers..period.