MANPATH in /etc/env.d/00basic ?

[ProGuy]

As I am using /usr/local for various programs, and therefore have som man pages in /usr/local/man, I am wondering why MANPATH is defined strictly to /usr/share/man in the 00basic environment file.

Shouldn't that path be specified in /etc/man.conf (where /usr/local/man correctly is places)?
I know that it is simple to correct this locally, but is there any reason to set MANPATH explicit?
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//ProGuy