The problem is that without tools and processes to systematically validate those result's people might be perfectly happy about completely inaccurate results.

I know i have had to correct one in three excel sheet i have ever gone over using pen and paper in order to validate the results but i am a paranoid sod who actually do this kind of exercise on a regular basis.

almost all of the disciplines known to rely on excel have a serous issue with repeatability of results either because nobody ever attempts it, or because it's a messy field without a well defined methodology.