I'm 15 and bought a Z because they're cheap which means i can justify running the piss out of it, and when i breaks down i actually know how to fix it (for the most part). The engines in them are so simple and are strong motors and on top of that there is so much room in the engine bay you could put anything you wanted in them.
The Datsun 'family' is amazing people will go out of their way to help you out which is awesome. Everybody that owns a Datsun honks and waves at fellow Datsun owners. Hybridz is around..(anything you could dream of has either been done or talked about.)
And they have so much character that you really cant get with any current cars (meaning they look #$^@#$^ amazing!). They're fast cars (they keep up with muscle cars) and even if they beat you in a straight line once you get out on some curvy roads you'll loose them in a heart beat.
Last reason is because I could afford it on my own no help from my parents (Money wise and also mechanically i basically got no support other than "it's alright if you bring it home")