Oh, when I was younger I was mesmerized by watching all of the little squares in the defrag tool change color and move around. It was like someone tidying your room for you!
As recently as 2015 I was advising people that if you finish your work too early to go home, you should spend your time on updating our docs, defragging your hard drive, and reading the docs for your tools (eg, learning keyboard shortcuts or optional flags).
Defragging is one of those clear cases for time shifting things from your high value time to your low value time.