They have mentioned a few times that it is to reduce spam. See: https://github.com/signalapp/Signal-Desktop/issues/2383#issuecomment-758085898 https://github.c

They have mentioned a few times that it is to reduce spam. See: https://github.com/signalapp/Signal-Desktop/issues/2383#issuecomment-758085898 https://github.com/signalapp/Signal-Desktop/issues/2383#issu... and in this paywalled article https://www.sueddeutsche.de/wirtschaft/signal-meredith-whittaker-whatsapp-messenger-datenschutz-1.5652005 https://www.sueddeutsche.de/wirtschaft/signal-meredith-whitt... where they roughly say >We are currently working with high priority on the fact that you can assign usernames and hide your mobile number. However, it will still be necessary in order to register. There are several reasons for this, including the fight against spam.