Both Gmail and Outlook keep asking for a phone number for security purposes once in a time, when you log in.
Now, I decided to use two factor authentication via a phone authenticator app for both. Gmail seems to have a phone number as a mandatory requirement for using 2FA.
From my perspective, I don't think a phone number should be a mandatory requirement for the 2FA service. If you use 2FA, I think you're responsible enough to keep a recovery code stored at a safe place. Moreover, I find it infringing on my privacy.
Why does Google ask for a phone number as a mandatory requirement for using the 2FA service?
Furthermore, if you're logged in through your smartphone, there already exists a prompting feature. This seems to make the phone number requirement a bit redundant.
It is the mandatory requirement that I disagree with. They diverge in this policy from Microsoft Outlook and Attlasian's Bitbucket, for instance.