This isn't the first time Google ditched its single sign on system. Remember Allo? If I had to guess, this disaster had the same root cause. Somebody looked at

This isn't the first time Google ditched its single sign on system. Remember Allo? If I had to guess, this disaster had the same root cause. Somebody looked at how WhatsApp (or in this case, Paytm) took off in India by using the phone number as ID and decided the way to get more users was to copy that aspect of it, skipping any migration plan to get to market quicker. This alienates all the existing users of Hangouts or old Google Pay in currently high value markets, and nobody at the company cares enough to stop it.