You're asking the question in a way that's unreflective of how people think. They can do it and want to do it and would need a reason to
not do it. So the question is, what would make someone feel like they were ethically compelled to watch an advertisement? It sounds impossible to me, maybe someone with a very unique perspective could chime in about themselves.
Here's an attempt at a double-negative answer: you can't be ethically compelled into an unethical contract, and since advertisements are manipulative, voyeuristic and seek to take advantage of the limitations of human attentional control, it's a priori impossible for watching an ad or downloading a tracker to ever be ethically compulsory.
