[wolverine876]

Signal is moving away from phone numbers, developing the components needed to securely provide service via user IDs.

My understanding is that their intended audience is the general public, not crypto-security geeks, and as part of that they wanted integration with existing address books. With a small team, developing all the security and usability was more important than eliminating the phone number piece.

They apparently don't retain any data but the phone number, and I think the registration date and last logon date.