Why aren't we already? It's new, unproven and most of us haven't even heard of it yet. A quick glance at the website suggests you have to install a native program, which, compared to a web app, adds friction, makes it harder to use and requires trusting the authors with full access to your computer. There isn't a mobile app. OS X support is "only lightly tested".

And, even if none of that were the case, the most important reason we aren't using it already is because the people we want to talk to aren't using it, either. https://en.wikipedia.org/wiki/Network_effect