OS X 10.9 Mavericks is currently run by more than 15% of mac users.
Released on October 22, 2013, Apple’s OS X Mavericks is already running on an estimated 15% of macs, a number that had taken its last operating system more than 3 times as much time to attain. The principle reason the quick acceptance? Mavericks is offered to Mac users completely free of charge.
While it may seem bizarre for a company to be giving away software for free, there are several short and long term benefits that can come with this decision. As already demonstrated, it has attracted the attention of many of their consumers, causing them to feel a sense of loyalty for receiving the update without paying. For Macs that had been running older operating systems, running Mavericks may open up their availability to the newer software that Apple offers through their App store which could generate future sales. The update could also lead to hardware updates for Apple as the update could require more powerful hardware than some older macs are equipped with.
Having a united and uniform product to cater to facilities Apple the software design process and ultimately leads to better service and products for its customers.
Sources:
https://www.gosquared.com/mavericks/
http://www.zdnet.com/apple-makes-os-x-mavericks-free-the-implications-7000022288/