I understand your point, but it still doesn't make sense when compared to traditional way of using Credit Card.
You provided situation about what if the phone is stolen. My question to you is, how will it be different from Credit Card being stolen? In my understanding, if Credit Card is stolen, we call the provider to deactivate the account ASAP. In terms of phone being stolen, this process can be applied.
About your other reason of stealing information, the device can have at most the same information in its User Interface as the Credit Card itself. In fact, it can restrict displaying info such as expiry date, CVV, and even the account number, but still send them through NFC for payments. So I don't get what exactly someone else can steal from iphone which they cannot steal from the actual plastic card.
Bottom line, we are already using tap to pay in our credit card which doesn't require any PIN or signature. Someone can steal the plastic and start tapping, which is why there is a lower maximum limit which reduces risk. Thus, I do not understand what exactly Apple's security is trying to accomplish which the actual plastic card already has. My understanding is, the usability should be equivalent to tap to pay, otherwise Apple Pay will only be a gimmick not bringing additional convenience than using the card.