Same reason why I am absolutely terrified of playing any instrumental music on Spotify. I let one track run till the end and my next 2-3 discover weeklies will be filled only by instrumental music.
with youtube i usually open a video in a incognito tab anytime im watching something random, otherwise it takes weeks of clicking "not interested" just to get rid of some recommendations. sad times
So after I watch that instrumental music video, there will be a mass recommendation for other instrumental music. And that's nice, because I apparently was in a mood for that. And the next day, I open my browser again and they are all gone! I can dive into the music for the mood of that moment right away.