A related exercise that may be of interest: five levels of "why."

Find a willing friend or coworker, and ask them why they did something with a project of theirs. When they answer that, ask them "why" about their answer. Do this a total of five times.

After the second "why," they'll probably have to think pretty hard. The fourth or fifth "why" sometimes elicits a "because it's just done that way" or "I dunno" response.

Then let them do the same to you.

It's a fun exercise.