Comment by donmcronald

It's 100% about linking identities between services. I've had my cell phone number for 25 years. It's basically a lifelong identifier at this point and I constantly have to use it for low value online accounts. I wish I could go back 10 years and get a dedicated phone number for online verification.

The security side is a total lie as well. Your post made me think about the biggest risk for myself and, like many people I know, I put my email address on my lock screen so that if I lose my phone someone can get it back to me. Now it just clicked for me and I realize I need to change that because if I lose my phone someone has everything they need to recover a lot of my online accounts. My Google, Microsoft, Amazon, etc. accounts all use that same email address and all they need to do to perform SMS recovery is put my (unlocked) SIM in another phone.