People use Windows to run Windows applications. They use Android to run Android applications. Whether they would use it for the GUI and experience or not is secondary, they don't have much of a choice anyway. If an OS cannot run Android applications -- and AOSP cannot do that since many applications rely on the proprietary Play Services -- it is not Android.

That Android would be free if you replaced the non-free parts by free ones is obvious and does not make it actually free.

> Also many people buy windows license separate from their device. Google surely does not want situation where people buy google services license... they want mass adoption for data collection.

> If google starts to charge for android then i am sure there will be manufactures selling phone without OS.

None of this matters for the question at hand which is if Android is free.

People using also Android for GUI/experience. Google controls the Android system. They have a large say how Android Apps should look like and are consisted of.

At 2018, talking about yet another Mobile OS beyond Android/iOS is just pure nonsensical fantasy. The game is over, if Google going to charge Android, the manufacturers will not be happy, but they will pay and pass the cost to consumers.