I came here to say exactly this. We host a Slack team for local freelancers, and I'm part of a few communities.. and I currently can't imagine me using two different clients for this (2 desktop apps, 2 mobile apps, 2 admin web apps). So, Slack it's gonna be.
We had non-interoperable web services, and then businesses offering aggregation of those (like various social media aggregators, or even Slack) had appeared.
