I think this document would shed a lot of light on the topic for you....
With that said, the "campus design" is not all encompassing, you have SONA (which can be reviewed here: http://www.cisco.com/en/US/netsol/ns629/index.html ) that ties in all of the different pieces.
You have different designs for different "modules" or "pods" of your network, and then you have the overall architecture guides that explain how to tie in those various pods to form a resilient, available network.
As with all Cisco designs, they build in a lot of redundancy, because everyone wants the Five Nines - 99.999% availability. However, when the budget finally gets drawn up, that is usually a matter of debate - do we need that? That is where business justification comes into play.