[pjmlp]

There were some statements that they were updating the Play Store contracts to impose this, specially after GSI.

Because the uptake from IO to IO has been diminishing, as Android is already good enough for the purpose of selling phones, so most OEMs aren't even bothering with Treble (Android 7+) for new devices, other than flagship ones.

So Google is now forced to do exactly that if they want OEM to actually care about new versions.