[jmkni]

From a developer perspective, the Google Play Services are so damn convenient, and they work well.

When it comes to push notifications in particular, I don't know of an alternative which works quite as well as Firebase (if there is, please tell me!)

It seems like developing apps without the Google Play Services will take longer, and be more expensive. Maybe that's just psychological, but it's risky to decide not to use them, especially when you are time constained/on a budget, and you know how to use them etc.

[zuron7]

There isn't. I have had to self host Gotify to send myself push notifications cos some proprietary apps do not have support to keep an always on connection to the server.