I was surprised to read that "Google has struggled to create such network effects with both Hangouts and Messenger." At my university, all the student groups that I have worked on use Google docs, Messenger, and Hangouts to coordinate. We don't use Messenger a lot, only when we are online working on a document together, but we do use Hangouts weekly. For us, Google is for group productivity (sort of like Slack), but…
A few other students at my university use Hangouts and Docs, but generally everything is done via email and github.