This is something I am running into more and more frequently. The clerk asks you to sign both the credit card slip as well as the cash register receipt. Presumably, they need to keep the signed cash register receipt to deal with chargebacks. There could be an opportunity here for a payment provider to offer a better service to retailers so that they don't feel they need to do this.
Even worse, the other day a major (and reputable) retailer in Singapore actually typed in the CVV number on my card that proves that the merchant did actually see the card. The number was typed into the POS terminal provided by the merchant's bank, so the bank is involved in this.
Why aren't payment providers solving these problems for merchants in a cleaner, more convenient way?