[Daniel_sk]

They have been too busy with integrating crypto payments instead of fixing long standing issues or planned features (allow to register without a phone number). But - to Signal's defense - while you can scrape the phone numbers, there is not much you can gain from it, you can only tell that a specific number is a Signal user. And sometimes you can see the username (if the user chooses to not encrypt it).

[walrus01]

Given the re-use and re-issuance of phone numbers in very busy US area codes (like 212, 202, etc) it also only allows discovery that at some unknown point in the past, that number has been registered as a Signal user.