Something strange happened when I grew up.
Phone numbers as identity
As a high school student, I gave my email address readily, and reserved my phone number only for people I actually wanted to communicate with. Email was (still) easy to filter and ignore; I only logged in once a week and seldom replied to anything. I was most readily reachable via phone.
Phone numbers usually came with contract plans; they were non-portable, each change meant mass-messaging one’s new number to one’s contacts. At that age my peers changed email addresses on a whim, and phone numbers were our only constant.
Emails as identity
As a working adult, things have changed. Now I give my phone number readily, and my personal email address seldom. Phone calls are easy to ignore, especially with a phone in vibrate-only mode.
Emails are still easy to filter, which makes it easier to sort personal correspondence from spammy fluff; it is phones which have become unfilterable, with a UPS delivery call being almost undifferentiable from a telemarketing call.
I have had more than a decade to grow into my email identity, and wouldn’t let go of it for all the world. My phone number now comes from a prepaid plan, because I don’t call often and like the freedom of being able to switch telco service providers on a whim. I use mobile broadband much more often than I use calltime and SMS messages, especially with WhatsApp, Facebook Messenger, and other messaging services fast replacing them.
The phone number now becomes an impersonal collection of figures, reflecting little personality, while our email carries the collective baggage of everything that has happened to us since we decided on that strange text string to identify ourselves by.