Web forms allow social media sites to capture bare phone numbers and store them in other places than just for authentication services. The places they store these numbers are often exposed to the public and to partners for a fee, along with personal data, which regularly is connected to other personal data on each account user. 2FA does not keep your account secure, and is just a bogus ploy to get your phone number, by social and other platforms) if most of your personally identifiable information on a site stores can be scraped ALONG WITH YOUR PHONE NUMBER, as it was, from a social media site (Which is exactly what happened in the original article cited).