I’m pretty sure it’s for security reasons, it allows the app to ensure the code comes from a correct Signal phone number and not from a third party actor. It’s hand holding yes but it’s a trade off in favor of non-technical users.

Somehow all the other apps, including bank apps, do not seem to consider this necessary.

Signal always has excuses, "we can't add usernames because we don't know how to make them secure"

> it allows the app to ensure the code comes from a correct Signal phone number and not from a third party actor.

But if they sent you the code, even if a third party actor could somehow see it and hand it to you instead -- so what? What's the difference?