This strategy is completely opposite to that of their biggest competitor, Apple. Apple only puts iOS on Apple products. iOS is a closed-source system. Since it is restricted to Apple products, the adoption rate of the iOS is limited simply due to market constraints.
The open-source initiative that Android is based on has allowed the operating system to thrive in a competitive smartphone market. Google has become a major player in the smartphone environment, in less than a decade, due to their excellent implementation of open-source fundamentals. Without open source software, the smartphone market would look very different today.