Everybody in the replies asking why FB wouldn’t build SMS themselves seem to think it’s a 6 month project & this cost would go down drastically if they did.
WhatsApp has been on Twilio for a decade & only moved more messaging to the platform over time.https://twitter.com/loganbartlett/status/1258765792633643011?s=20 …
Sending SMS around the globe with reliable delivery is very, very difficult. It requires an insane number of telecom deals + good infrastructure. There are hard SMS costs below the surface, which FB surely gets a nice discount on, and you have Twilio’s dozen years of experience.