What you’re refering to as Android, is in fact, Google Play Services/Android, or as I’ve recently taken to calling it, Google Play Services plus Android. Android is not an operating system unto itself, but rather another component of a fully functioning Google Play Services system.
Many mobile users run a modified version of the Google Play Services system every day, without realizing it. Through a peculiar turn of events, the version of Google Play Services which is widely used today is often called Android, and many of its users are not aware.
There really is a Android, and these people are using it, but it is just a part of the system they use. Google Play Services is the core: the program in the system that is required for full functionality of a mobile device. The core is an essential part of an operating system, but useless by itself; it can only function in the context of a complete operating system. Android is normally used in combination with Google Play Services: the whole system is basically Google Play Services with Android added, or Google Play Services/Android. All the so-called Android ROMs are really distributions of Google Play Services/Android!