Why /usr/local/bin /usr/lbin /usr/man/various-dirs

[Jan B. Andersen]

As relative new unix user/admin on BDS and Sys V systems from different
manufactures I find it very inconvinient with all those different names
and directory structures. Why do some unixes have /usr/local/bin, while
other has /usr/bin/local (and src) or /usr/lbin ??

And they all seems to have their own convention as to how /usr/man should
be organized. Some has /usr/man/man[1-n] (and possibly /usr/man/manl),
while NCR has no /usr/man at all! They have /usr/catman/man_[apu]
instead!

Another thing which I have noticed is all the different flags and dirs
that /etc/install does or *DONT* accept. Why do it have to be this way??