[CentOS] Documentation question

Apologies if this is a FAQ or it's simply due to a lack of volunteers. 


I'm curious why the CentOS Documentation here: 
http://www.centos.org/docs/5/

...stops at CentOS 5.5.

And also why there is no: 
http://www.centos.org/docs/6/


*** Curiosity killed the cat. ***


Thanks, 

Nate