Fair enough. But people will decide not caring even slightly about binary size is admirable (move fast and make users buy new phones, I guess) and eventually everything will be huge. Already the number of sub-60MB apps is dwindling and the 100-and-up club is growing, if my recent updates list is any indication.
That's intentionally awkward. If I tap the messages icon on Facebook.com on mobile, I get redirected to a page telling me to download the app. Similarly, messenger.com points me to the App Store.
On the contrary: You can even enable push notifications with Chrome for Android. Chat included. I haven't touched the native apps for ages and everything works just fine.