Why “less AND more” is the answer

"Less is more" is a popular idiom. It sounds fancy, but less of what? And more of what?

As a beginner guitarist, you struggle to play the notes perfectly. Because of extraneous finger movements, your speed suffers too. But as you become better, your movements become smooth and imperceptible, and you're able to play at the right tempo. What has this got to do with "less AND more?"

By becoming more economical, you're able to "play more" (speed) with "less effort" (movement). You're getting more output for less input. Why not apply the "less AND more" principle to everything else too?