Large corporations will buy messaging / social networks over time because of the fact that there is a long tail for people who will use the service. The perception that app X is "uncool" or has no growth is the fact that being a part of HN makes you think that the bleeding edge is whatever everyone uses. Of those other frameworks there are a multitude of users on those platforms. The perpetual buying of these companies is a part of the Red Queen hypothesis that large megacorporations have to adapt to survive. One way to do this is the purchase of companies and messaging and social have so much cool platform churn that it becomes endless.