I asked the gal at Sam’s about it, and she said “Its to make sure that you have all of your items”. (A good response - no doubt learned in training).
It would be fun to cross-reference this thread with the thread about the Home Depot policy of not chasing shoplifters!
Now the one that DOES get me mad is that I have to get my psudephed from the pharmacist! (Sure - your store is open 24 hours, but the pharmacy is open like 10:30a - 3:30p on the weekend!?)
Costco had a similar policy at the exit,..they actually showed me where they had double charged me on a case of Cokes and I went back to get another. Under the cover of Quality Control, they doubled as disincentive for shoplifting. It also helped keep the checkers honest.