tap done.

No handing cards, picking up terminals, signing receipts, checking signatures or any other nonsense.

It's also secure--tapping is chip compliant.

You can also have more than one card on your phone.

I give my card to the cashier, they swipe it, I then wait for a receipt to print, wait for the cashier to hand me a pen and the receipt, sign the receipt, hand it back to the cashier with the pen. If they're doing it right, they compare the signature to the one on the card, but in most cases I am then done.

versus

I wait for the onscreen prompt, I tap my card, hear a satisfying beep and am done.

It's pretty obvious the difference.