I think this weird anti-self-checkout crowd is just young people who don’t remember the times before self-checkouts. Even if every checkout was manned it was still completely normal to wait upwards of ten minutes, even when it wasn’t that busy. I remember my Mum excitedly running to a checkout because there was only one person queueing there. Nowadays I totally expect there to be no queue at all and I feel hard done by if I have to queue for more than one minute.