Why we can download MacOS X 10.7, 10.8, but not 10.9?

Hello, so there is a small problem, I really need the .dmg file of OS X 10.9 (Mavericks) that is because in Catalina (10.15) My Mac turns on very slowly (takes like 2 to 5 minutes to boot, instead of 1, or 30 seconds) and I really like skeumorphism, and that's also the last OS X version with skeuomorphism. I do not care about that is doesn't have support anymore, I just use my Mac for basics (iWork, Internet stuff, and VirtualBox). I only have installed the basics, just Keynote, Pages, Numbers, iMovie, WhatsApp, VirtualBox, and nothing else. So again, why we can only download the .dmg's of Lion, Mountain Lion, Yosemite, etc... but not Mavericks? Mavericks is my only option, it is one of the latest versions with skeuomorphism (cuz it's beautiful), and is runs very well on my computer. Here are the specs of my MacBook:

(by the way, if anyone has a Mac disk image of Mavericks, please post it on this forum so it's downloadable for me)