There are many other tools besides receipt checking. Security tags that sound alarms at exits, paid stickers, video cameras, security and other staff observing shoppers, making expensive or easy to steal items inaccesible without staff assistance, putting all cash registers near exit, customer pickup areas for valuable items, etc.
If store staff observes an individual picking up an item and attempting to leave without paying they would have probable cause to detain the suspect or, I suppose, ask to see a receipt.
Most stores do not check receipts and shoplifting is not putting them out of business.
Even THAT should be stopped.
There's no excuse for the receipt nazis.
If people KNEW what WalMart did to them with the Cameras they'd never ever shop there.