Because of models-
For someone born in '68 and raised during the stylistally stagnant 70's and 80's (with exceptions), I know an awful lot about old cars, because I've been building them, talking about them, researching them for my entire adult life. My father was born in '44 and grew up wrenching with his dad in the mid-to-late 50's and early 60's and is a great source of vintage automotive knowledge, but I seem to impress him pretty frequently when we're at a car show together or whenever he's checking out my latest models. Which I gotta say, is a pretty great feeling.
I owe a lot of this knowledge to you guys, who help out and inform whenever possible. Much appreciated.