SMS costs money per message and this alone means it's a non-starter. Besides, phone numbers have other issues:
- The security, and the continued existence, of your phone number is wholly dependent on your carrier. You can't take it into your own hands.
- Phone numbers are tied to countries. This is a problem for people who travel.
- You can't self-host a phone number.
- In many countries around the world, a government-issued ID is required to buy a sim card, which means no anonymity whatsoever.
@grishka @dansup all th eabove is true, however, if it were -optional- users could choose to register on a server that does not have this as a requirement. There are thousands of servers,most of which may not need or want these options. That doesn't mean no-one wants these options.