If you hand your card to bar staff and they use contactless payment then you might want a receipt. Especially if they don’t ask to use contactless or don’t show you the amount. This is unfortunately far too common.
The receipt you get may not be a customer receipt. It is often a copy of the merchant receipt. The merchant receipt has your full card details on it. The card number isn’t part blanked out as with a customer receipt.
Make sure you check your receipt and destroy it if it contains your card details.