Why.
It’s the explanations people seek.
It’s the reason things get done.
It’s the motivation people need to take action.
It’s everything.
Carl Braun (of CF Braun & Co) came up with what I think is the best business rule ever:
You will be fired if you ask somebody to do something and you don’t explain why.
(He kind of said that … he said you could be fired on first offense, but second offense you will be fired, although that doesn’t jive with my story)
PS – This guy wrote a much better article about ‘why’ than I did, which you should read.