He lives off The Blueprint and Jigga is much more mainstream. He is a business man and knows which trends to hop on and which trends to leave. Buy when its hot, sell when it is cold.
Nothing wrong with Jay's MO.
Nas is viewed as a purer artist so he will live off more off his own artwork, especially since some of it is excellent (Illmatic). Besides that, It wasn't Nas that had the idea for the documentary, it was his fans that felt connected to it.
Personally I grew up in SW Houston, I can connect with Illmatic because I know what it is like to live in the hood and try to grapple with it at such a young age.