I read an article in ICS Cleaning Specialist mag about the six reasons people clean.
I did know them but never took the time to think about them. Howard Partridge, a seminar presenter for the cleaning industry, did a good job of listing them out.
1. Events - (dinners, graduations, etc.)
2. Visible Soil
4. Health issues
5. To Solve a Problem
6. Odor removal
A brief synop is given here but for the article pick up a copy of ICS magazine or go here to read it.