You don't need to use phone numbers as identifiers to upload contacts. For example Hangouts (RIP) and Matrix both support letting people find you by number with

You don't need to use phone numbers as identifiers to upload contacts. For example Hangouts (RIP) and Matrix both support letting people find you by number without using it as a primary identifier. I assume that using numbers as identifiers has two main benefits 1. easy (insecure) auth 2. it forces everyone to provide you their number so that lookup by number works better. Of course I don't find these worth it. I have had 5 numbers so far and there is a decent chance I will switch numbers again. I don't like having an identifier that is tied to my physical location.