Quantum Forest

…or at least a shoplifter. That seems to be the theory behind the policy of supermarkets and shops with a ‘you agree to show us your bags’ sign at the entrance.

Yesterday, I went to Woollies and took my own shopping bag (as I have been doing since 1994). I had the following dialogue when I finished passing the contents to the checkout operator:
—I’ll check your bag if you don’t mind—while starting opening my shopping bag.
—I do mind—while trying to close my bag.
—It is the store policy to check the bags.
—I don’t care about the store policy.

Why does people accept this policy or even volunteer their bags to be checked? Why do shops treat customers like petty thieves? Either they can prove that someone is shoplifting or they just should leave people alone.