Everyone having a phone already is orthogonal to whether or not it is a good idea to require phones to function in society. I don't see it as a slippery slope

Everyone having a phone already is orthogonal to whether or not it is a good idea to require phones to function in society. I don't see it as a slippery slope argument because almost everything will eventually move to being online-based, and if "having a phone" becomes the standard for authN, then someone without a phone is excluded from participating in all of those things.