On Sep 5, 2017, at 11:06 PM, Steve Johnson <scj@yaccman.com> wrote:

One day, I was attempting to print out a one-page document.  I ran troff piped into the phototypesetter and got out my roll of paper and fed it into the developer.  Out the other end came a page with only one line on it (beautifully typeset): "cannot open input file xxx"   A number of others had similar experiences, and stderr was born…
I hear you.   Postscript lacked the concept as well.   I remember spending bucks on a phototypesetter run just to find an error message as the only thing on print run.