Requiring mobile numbers is still a flaw. Calculation is "make mobile phone number optional and have most of the users refuse to give it away because they know

Requiring mobile numbers is still a flaw. Calculation is "make mobile phone number optional and have most of the users refuse to give it away because they know better and miss profit opportunity or make it mandatory and risk having a few fringe users use worthless numbers", so optimal profit per user is the chosen way when the company is driven by maximizing their own profit (actually shareholders) and do not care about people, communities and such.