Because given away for free to generate traffic on google properties, therefore Google will not ship features in Android that would be detrimental to the monetization of an android user by allowing them to control their privacy.
Personally, given the existing complexity of Android I find it funny that they said it would make things too 'complex' to give users control of their privacy.
Personally, given the existing complexity of Android I find it funny that they said it would make things too 'complex' to give users control of their privacy.