I use the parable of oil pressure gauges quite a lot in my training lectures on business intelligence. When you own a car without a pressure gauge, so long as the warning light isn't on you drive around quite happily, not paying it any attention.
Fit an oil pressure gauge, however, and everything changes. You are now constantly looking at the needle, worrying whether it is too high or too low, and completely unable to do anything about it - unless you are in the habit of carrying a fully equipped workshop around with you.
