No one is stopping the store from getting its merchandise back and banning them from the store. They've got a big carrot--cooperate and we won't call the police. Most chain stores have security; that's their job. Why involve the police for a CD or $5 pair of earrings?
Why? To provide a deterrent, that's why. Stores carry insurance for theft, but like all insurance, there is a maximum benefit. After that benefit is met, the rest of the loss is on the store. To help recoup some of the losses after that, they increase the price of their goods, and the rest of us have to pay for it. A little personal story here.
Years ago a middle-east family bought (or leased) a store around the corner from me. Because it was so close to my home, I frequented the place. One day when I went in, the police were there advising the store clerk about something or another. When they left, I asked him what happened? He told me some drunk came in, took several packs of cigarettes off a counter display, and just walked out of the store. The police told him if he comes back, give them a call, and they'll kick him out.
We got to talking about the growing theft in our area, and he was a young guy, around 18 years old. His grandmother wrote him and asked how his new life in America was, what goes on here and those kinds of things. So he sent her our local paper. She wrote back with great concern. She said our little suburb had more theft and robberies in one week than the entire middle-east has in a year. I asked him if she was exaggerating, and he said no she wasn't.
He said where I'm from, vendors have outdoor markets. They place tables and chairs for customers to rest while shopping. If a woman leaves her purse on a table and forgets about it, everybody crosses the road to make sure they are nowhere near it. In fact if she didn't realize she left it there until the next day, it's likely it would still be there.
In my country he said, if you are caught stealing from anybody, the police cut off your hand, and not in a hospital either. Get caught stealing again, off comes the other hand. He said there is no third time.