same amount of effort

Physical effort, yes. Cognitive effort, no.

• Intros on a serial show are expected, and in some cases change subtly from one episode to another to provide additional entertainment value (eg the Simpsons intro). In other cases a change of intro sets the setting for the episode (eg Star Trek: Enterprise's Storm Front episodes).
• YouTube ads are not related to the show, provide no contextual value, and in the case of interstitial ads are not even at a predictable time. They also tend to be inanely repetitive, showing the same ad over and over in consecutive videos. Contrast those to eg halftime ads at the Superbowl broadcasts, which have predictable timing, variety, and have a history of being (or trying to be) entertaining.