Why Is It Important To Optimize Images If You Can't See The Result?

In episode 188 of the weekly Hump Day Hangouts by Semantic Mastery (https://www.youtube.com/watch?v=z4hjG1D0WXQ), one viewer asked about the importance of optimizing images if one can't see the results.

The exact question was:

Hi Guys!

Question about Photos.

I optimized an image with a title,tags,description,geotag on my computer. ... https://www.youtube.com/watch?v=4bKzD4oYNGE