To be fair, Microsoft asked for licencing fees for ActiveSync used with Gmail. Of course, Google is not going to pay that for the free users, while Gapps users

To be fair, Microsoft asked for licencing fees for ActiveSync used with Gmail. Of course, Google is not going to pay that for the free users, while Gapps users have that included in price (the legacy free Gapps users aren't getting ActiveSync either). There could be another way for Apple to support push email - they could support third party plug-ins providing protocol support for Mail.app, so Google could implement Gmail support, fastmail jmap support, etc. It is exactly this way, how Gmail app for Android supports ActiveSync.