I think this comes down to the age-old adage of "If it ain't broke, don't fix it". We run 5.004.04 at the place I work at; it runs the scripts and does the job we need doing perfectly well.

From a tech perspective, the scripts we run on a daily/hourly basis are far too critical to risk having them not work for even one iteration. I think that this is the major, and most compelling reason to not upgrade. "What if it goes wrong" is something too terrible to even consider.

While I agree that a later version would probably be more fun to play with, and maybe faster, and more secure, it's more important to get the job done right than to keep at the cutting edge of new, at least in my experience.

Just my thoughts ..
--Foxcub