Of course, as long as you know the correct password and signature, of course, if the store staff suspect that you are using someone else's credit card "illegally", they will probably call the police, even if you can't provide proof that the credit card is yours, then you will be in trouble.

Because strictly speaking, credit cards belong to banks, and banks only allow cardholders to use credit cards. Strictly speaking, non-cardholders have no right to use the card.