All those things you list are a detriment to the merchant since they all hold up the payment process (longer checkout lines, disgruntled customers, etc.) as wel

All those things you list are a detriment to the merchant since they all hold up the payment process (longer checkout lines, disgruntled customers, etc.) as well as potentially giving the customer incentive to back out at the last minute. If I were a merchant, trying to sell me on the above "features" would pretty much convince me not to take part.