slight OT: shell-script programing style -- origins and change?

[Linda Walsh]

This is not exactly bash specific, but I was looking at a shell script 
recently and they use the age old convention of using upper case 
names for all their shell variables.

At one point I remember this being common practice, but today, ALL 
CAPS LOOKS LIKE YOU ARE YELLING OR ARE A FOUR OR FIVE YEAR OLD WHO
DOESN'T KNOW HOW TO WRITE.  (Blech, sorry..).  If you thought I was 
yelling, I made my point.

I was wondering where this convention came from  and  if it's still 
considered 'the gold standard' of shell programming.

Personally, there are some legacy variables, maybe system wide
environment variables like USER, and HOME, that make sense and don't
"feel" wrong in allcaps, but for user programs, I'm not sure
allcaps is all that desirable.  Maybe for 'constants'? Even there,
$phi, looks just fine or $pi...

What do others think, (or is there a better venue for this 
question?)  

I thought I 'd ask here first, since bash seems to be
the most advanced and most widely used descendent of the original
Bourne shell, and those most interested in that shell might be
on this list...but that could easily be a misperception on my part.

-linda