Everything we do, whether we are conscious of it or not, has a purpose. Why are we doing what we are doing? "Why" helps clarify and define purpose and therefore planning, decision-making, and follow through, especially when facing challenges. "Why" can be used negatively as a criticism, but it is still a very important question. Even if the asker is presenting a challenge, we are well served when we can offer an articulate (non-defensive) answer.
But when our purpose changes, our actions must change also. If not, then both will become meaningless and without essential energy and power. Purpose determines the quality of the destination AND the journey.