Hasn't that battle been lost for a while now though? How many different services have linked phone numbers with email or some other handle? (Particularly for 2FA)
On the few accounts I've been required to use that require a phone number, I've given them one. It just happens to be one from a modem phone pool.
I'll worry about what problem that may cause when it becomes one. Usually, these are for stupid things required for some project or another and the need for them is time-limited. I will not use FB, and have a pile of Twitter accounts with no phone numbers attached if I ever have reason to care about that.
And at the rate we're destroying trust in the phone system with spam, I don't think anyone will expect pickups in a few more years.
Quite many services require phone numbers. But services like reddit, GitHub, lobste.rs, or hacker news don't. Twitter has been in that list itself, but now is outside.
