The purpose of this standard is to replace Google's FCM push notifications so that you can receive push notifications on a mobile device for a bunch of services while only needing to maintain a single low-overhead connection.
This exists to improve battery life and decrease data usage for android users who don't use google services or prefer to host their own. And generally it exists to provide a standardised, independent, privacy preserving option for users and app developers.
Neither RSS nor email solve this problem and actually this specific service would be the exact type of service you'd use to notify the user's device that the apps that use RSS or email have new content to fetch.
This exists to improve battery life and decrease data usage for android users who don't use google services or prefer to host their own. And generally it exists to provide a standardised, independent, privacy preserving option for users and app developers.
Neither RSS nor email solve this problem and actually this specific service would be the exact type of service you'd use to notify the user's device that the apps that use RSS or email have new content to fetch.