I've noticed a number of times that asking existing users to provide a password (if they are attempting to make a purchase) is causing lost sales.
They don't remember their password, can't access it fast enough or another reason.
A fix would be that if people are trying to make a purchase and using a credit card that this feature would be bypassed, as by providing credit card details is a good enough way to ensure that the person is trying to make a legitimate purchase.
Thank you for this suggestion! This feature request or some aspect of the functionality suggested is currently being reviewed for possible inclusion in a future update. If there is additional information, this post will be updated to reflect it.