Depending on the credit card system used, there's various levels of fraud detection. Some stores use a point-of-sale system for in-person transactions, and those generally don't need the CVV code because you're supposed to have the physical card. It doesn't stop some businesses from using the system incorrectly, allowing them to charge a card without a billing address or security code.

This is part of why credit card signatures are basically useless compared to a pin that's required for all in-person transactions.