The mother of all network effects. People ask for your phone number based on the PSTN format tel:800-NNN-XXXX. 0% of people have a sip:username@company.com. Suc

The mother of all network effects. People ask for your phone number based on the PSTN format tel:800-NNN-XXXX. 0% of people have a sip:username@company.com. Such a transition would rely on phone companies voluntarily relinquishing their control of the address space, spending huge sums of money on training customers, to de facto commoditize their service. Every single phone with just a number pad would have to be replaced. Hence this will not happen. You can already bypass the PSTN by using Facetime, Signal, Whatsapp, etc. But when someone doesn't use the same service or doesn't own a smartphone at all, good luck telling them to set it up or not contact you at all.