When I was in IT, the rule was 'no essential businesses processes in Excel unless defined and approved' to ensure 1. The formulas were actually correct and 2. We could provide continuity should the person leave 3. These items were included in corporate backups not just user level ones, etc. Hardly anyone followed that process. People are going to use the easiest/best/quickest tools available to get their job done. Add in promotions based on making 'big' cases and you have quite the incentive to abuse these tools without some huge conspiracy. Simple human nature.