

They fear Google more than they fear losing their account. Yet some people are absolutely convinced that if they hand over their phone number, all of a sudden Google is going to do exactly that, and probably more evil things they can’t even think of. Google will not use your mobile phone number to spy, track, or otherwise compromise your privacy.

It proves you should be allowed access to the account with which you associated that phone number.

ADD RECOVERY PHONE NUMBER TO GMAIL ACCOUNT CODE
Your ability to provide that code when asked proves you have the phone at that number.
ADD RECOVERY PHONE NUMBER TO GMAIL ACCOUNT PASSWORD
If an online service needs you to prove that you’re the account owner and you have the right to log in to that account, even if the password doesn’t seem to be working, that phone number you gave them is the proof they use. Even if you lose your phone, that number can be reassigned to its replacement by your carrier. As long as you maintain that number in working order, it’s how the people you share it with reach you. Your phone number is one small part of your identity. The reason email service providers want your phone number is very simple: when (not if) you have trouble logging into your account, that phone number can be used to verify that you are who you say you are. Sometimes, however, there’s a much more frustrating reason people fail to provide recovery information - in particular, their phone number. Without that proof (in the form of recovery information used to verify your identity), your account is no longer your account. One day, your account gets compromised somehow, and you have no way to prove you are the legitimate owner. In most cases, it’s a simple oversight with disastrous results. In one of my more important articles - A One-step Way to Lose Your Account … Forever - I discuss the sad reality that accounts are frequently lost because people fail to set up recovery information or keep that recovery information current.
