Most stores don't require you to show a receipt as you exit, nor have they until recent (last 15 or so) years. If they think you shoplifted something, they need to have witnessed you shoplifting and catch you as you leave the store. Automatically questioning one's guilt (or innocence) is a waste of your time and a theatre at best (I say this because the times I've let them check my receipt they haven't even carefully checked it against the contents of my bags). Therefore, it is actually waste of both parties time.

Even if you perceive it as a reasonable thing, there are many people who don't and who find it invasive as well as offensive. I find it disrespectful. If there's a legitimate security problem at a store, then, as a customer, that is not your problem and you should not be required to pay with your time. There is nothing wrong or illegal with refusing to comply with store policies such as this after you've given your money to them and done no wrong. We do not need to waste our time to suit a company (that doesn't have their security program together) 's wishes.

Detaining people unlawfully IS a crime, however.