That's the stated, euphemistic reason. The real reason is that they are doing security theater. Finding something you may have forgotten at the checkout is th

That's the stated, euphemistic reason. The real reason is that they are doing security theater. Finding something you may have forgotten at the checkout is the only possible benefit to the consumer, so they play it up as a point of customer service, to partially counteract the unreasonable queue they create for exiting the store. If the genuine concern was forgotten items, they would do the additional QA check at the point of sale, where the item is most likely to be found, rather than at the exit doors. Don't parrot the corporate propaganda without giving it your own analysis first. The veracity is easily checked. Buy a small, disposable item with your regular purchase, and put it in your pocket after checkout. If the receipt checker notices the item is missing, note a positive result. Put the receipt in your pocket with the item. Next time around, take the item out of your pocket and put it in the cart, and see what happens. Make sure you project the confidence that yes, that object in the cart is yours, and was lawfully purchased during a previous visit. Beware that this sort of testing may get your membership revoked.