system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does Google constantly redesign the layout of YouTube and Google Search?

I thought it was bad form to arbitrarily change elements that are familiar to your audience, such as the black bar that used to on top of the google.com homepage (and still is for some domains). Is there a Google-specific design doctrine I'm not getting here?
gpt
because that is how middle management proves they are of value. 

If the page doesn't change what good are all the analytics and UI guys. 

Managers do not win by maintaining the status quo, the relentless drive for growth means it will always be "evolving".