I know when I watch a TV show, large sums of money went into making the show I'm watching due to the history of television. Writers, actors, set builders, etc. were all paid during the production of a TV show and I know commercials and product placements paid for all of it.
When I watch something on YouTube, my first inkling is to think I'm watching some bloke with a webcam making a video in his basement. The history of YouTube causes me to think that the person on YouTube operates all by themselves just for the fun of it. While I know that that's not the case anymore the historic perception is still there, that's what the rules are meant to protect general public against.
YouTube creates a different kind of relationship between viewer and content creator, one that's particularly intimate and consequently persuasive.