[BoorishBears]

Because Google is trying to further consolidate/integrate Android and Google Play Services since they can update the latter a lot easier than they can update the former (gets around issues like carrier approval). More and more core features need features from Google Play Services and Firebase, and it's only getting worse.

[vmateixeira]

That's actually a very good reason altough I can foresee this getting messier if we consider backwards compatibility.

[BoorishBears]

It's a good reason but bad news for Android staying useful in it's open source incarnations since Google keeps Google Play Services on a tight leash