From what I've read so far, I get the impression, Gitter was purchased solely for marketing value. And in a lot of ways, is quite ingenious. I would suspect, 80% if not more of the discussions that occurs on Gitter, revolves around repos that are hosted on GitHub.

By tapping into those conversations, they'll probably be better able to identify GitHub pain points and provide subtle hints and nudges, for Gitter users to consider GitLab.com