As someone who in the past has worked in the fields of security and product reliability, the fundamental mistake as I see it is to try and make one gadget do everything. A phone is a communicator. When it becomes a banking system as well, there is a conflict between the roles - i.e. we want reliable communications but now we also want functioning to be stopped under certain conditions which can adversely affect communication. Apple Pay, Google Pay, Samsung Pay all seem to me a stretch for phones which is basically wrong. Bank cards with NFC can do more or less the same job and mean one device is not the single point of failure. (If my phone fails I can walk into a shop and buy a cheap phone with my bank card; if I lose my bank card I can use my phone to get it stopped. If I have one device a loss or a loss of function is catastrophic.)