"Why" Instead of "How" and "What"

The other day, when I was working on one of our "Do It Yourself" projects, namely the garage, it struck me once more that useful documentation will answer the question "why" rather than "how" and "what". The previous owner of our house had started and finished several interesting renovation jobs, but I wonder "why"? (And I donít have any documentation for "how" and "what" here either...)

If we transfer this little story to programming, it reminds me about that I think we should be asking ourselves "why?" when writing comments. If you also need to write comments for "how" and "what", it might be a sure sign of smelly code and an indication that you need to do some refactoring.