Benedict Evans, in his blog post titled “Mobile is not a neutral platform”:
Really, what we see here is a search for another run-time. We had the web, and then we added apps, and now we look for another. Notifications? Siri/Now? Messaging (as forWeChat in China)? Something else? But each of the previous run-times lacked search, discovery and acquisition as a fundamental part of the architecture – they had to be added later (and arguably that’s still not there with apps). On Facebook’s desktop platform, in contrast, both halves were there almost from the beginning. The next run-times on mobile might have both halves too.
Related to the notion that the importance of the homescreen is diminishing.