Nice note, Serra!
SMS was killed by over usage to communicate by marketers. Since the SMS was used more as a SALES technique, rather than a makreting technique, it is considered SPAM. On top of it, no control of the recipient on who can send an SMS (a non-existent Opt-in) killed the golend goose.
But with the need for AUTHNEICATING a person and the ubiquitous ONE TIME PASSWORD, SMS is back in play, that too a critical play.
So, the SMS is very crucial for the authentication, but for customer acquisiton, it may not be there at. But for transactional conversations, SMS works good. Of late, WhatsApp is trying to get into the shoes of SMS.
#My2satoshis