I have avoided self-checkout registers like the plague since their inception.
I don't want to get an argument with a machine over what item was removed from my cart and placed where and when every time I make a purchase.
Some stores have removed the self-checkouts, presumably for lack of acceptance. Other stores have dedicated an employee to monitor the self-checkouts and provide assistance to customers who have failed to follow the correct procedure. That employee is usually very busy.
If stores choose to ignore the preferences of their customers to improve profits by cutting low-wage employees in favor of machines, I believe their plans will backfire.
I envision near-future, robot-stocked stores entirely staffed by security forces dedicated to catching shoppers attempting to scam the automated system. I also see many of them succeeding.