Google is really good at coming into markets and offering a free product and in doing that sort of stymieing the development of alternatives.
Do you remember the cell phone market before Android? Phones were expensive. Phones were locked down. Not only did you have to pay for apps, you also had to pay for stupid things like ringtones. Android helped drive down the price of smartphones. Android helped sprout a ton of cheap phones & tablets that otherwise would not have a decent OS to run.