That still means running your own server, and having a machine running 24/7 to host that server. For many, many people nowadays a laptop is their primary and often only machine.
Saying is easy. But for some reason, it still doesn't exist.
With IPv6 one would suppose that it would be easy to keep the same address given that there is virtually no chance that anyone could accidentally be assigned it.
Similarly for Android, the most reliable notification method is using the Google Play Services servers.