> After some thoughts, we have decided to minimize redundancy in the NetBSD
> Packages System's documentation, and concentrate it on the following
> files:
> [...]
>  - pkgsrc/mk/mk.conf.example
> 	Variables used in the packages collection, likely to change
> 	often and fast, no chance to update this on a per-release base. 
> [...]

More to the point, pkgsrc is designed to run on the last release and -current. 
Any documentation that is stored under the src/ hierarchy is liable to be 
different to what is in pkgsrc/, and so will quickly end up being confusing at
best, incorrect at worst. Whilst this also applies to packages(7), in practice 
the values in that manual page change far less frequently than the ones in 
mk.conf.example. I still think there's a case to be made for having the 
pkgsrc-related man pages (indeed all pkgsrc documentation) in a separate 
directory under pkgsrc/.

In addition to that, mk.conf.example is just plain handy.