why can't I install Mavericks

I just bought a MacBook (early 2009 edition) and it upgraded right away to 10.8.5 without issue.
I would like to upgrade my machine to 10.10 which I believe is Mavericks but it doesn't exist in the App Store???!!!
Why am I not allowed to upgrade to Mavericks???

As each new version of OS X is released, all previous versions are removed. Only those who had purchased the various versions can go back to the Purchases section of the Mac App Store and re-download the different versions. 10.10 is Yosemite, 10.9 was Mavericks and 10.11 El Capitan is the current version available to you.