Part of the reason youtube ads are so annoying is that many of them are played at random times while you are watching a video. There is no smooth transition to the ad. When watching news or sports on television the announcers will say "And now we're going to a commercial break" and they play some outro music. Then they play some music to welcome you back.

When watching a sitcom or drama the script writers plan in the commercial breaks where you would have the different acts in a play. They are natural stopping points to take a short break.

Youtube ads are just random interruptions.