The point is cost savings for the supermarket. That's it. Some customer prefer them, but usually that is the effect of deliberately understaffing the remaining cash registers, or the customer being completely unable or unwilling to interact with strangers.

Supermarkets are now grudgingly admitting that self checkout systems cause a significant increase in loss due to theft, but that it is still cheaper than hiring actual staff for the registers.

In the Netherlands the current state of affairs in supermarkets with self checkout registers is that theft is on the up. People justify 'forgetting to scan an item' by the (perceived or actual) greed shown by supermarkets in terms of shrinkflation and the rising cost-of-living. Supermarkets did really well during the Covid-years, but customers didn't benefit from that in the slightest.

An additional problem is that the staff attending the self checkout registers are often young (because it is a position which would waste the skills of the more experienced employees), and they get bullied and berated by customers pissed off for getting selected for random (either actual or directed by the staff watching the cameras) checks.