[tex-live] gpg with tlmgr with tl 2016 pretest, etc, on a Mac

[John Collins]

At various points in this discussion, it has been mentioned that on 
linux it is recommend to install TeXLive as a normal user.  What are the 
reasons for this?  In the installation instructions 
https://www.tug.org/texlive/quickinstall.html the recommendation is 
merely stated, but no justification is given.  Why should this be 
different between linux and OS-X?

A quick Google search did not show an obvious place to find this 
information.

John Collins