Also, it's not 'disruptive' which isn't very sexy. At the same time, no one's really disrupted email (probably since gmail) and even sms for the most part, as a form of communication because they are the only cross platform with a very low barrier to entry. Note that all the sms replacement apps still use sms as a fall back since it's a shit show of walled garden apps.
I'm starting to believe that any idea of "disrupting" communications via a private company should be culled in its infancy. Market can't do infrastructure. Most companies will do their utmost to lock you in, and then abandon the product as soon as it's even marginally more profitable to do something else. Doubly so with Internet startups, for which the barrier to exit is incredibly low.
