That's true. However, just like any other third party library, app may use, but they don't have to. It is up to the developer. It is perfectly fine to develop A

That's true. However, just like any other third party library, app may use, but they don't have to. It is up to the developer. It is perfectly fine to develop Android apps that do not use Google Play Services. In fact, if you want your app to run on Chinese devices or Amazon devices, for example, you have to account for missing Google Play Services.