Well, he's wondering more why it isn't set than how to set it, I think. You don't say what distro you're using, but I think you're using one of those distros that doesn't really use MANPATH anymore, but reads man.config. IOW, can you access the man pages which are specified in your config file? Then you're okay. I think 'man manpath' (assuming it does
) may help on your system.