I am confident that an interface standard could be developed to allow some level of identity portability. Supporting such an interface would be rolled into the myriad other compliance requirements that tech service providers have to deal with these days. (A natural part of being in a maturing consumer facing industry.)

Cellphone carriers argued that number portability was too hard or too expensive.

"But cell phone companies argue counter that the idea of portability should be scrapped because customers aren’t demanding it. They argue that implementing portability, which involves retooling the software of each carrier’s computerized call-routing system, would be expensive and technically complicated.

“The cost to be able to move numbers from one carrier to the other is significant, and it would be significant for the customer too,” said John Scott, deputy general counsel for Verizon Wireless. “Our argument is that it’s not necessary to promote competition.”

Carriers Aim to Kill Number Portability - 2002

https://www.latimes.com/archives/la-xpm-2002-jan-16-fi-cell1...