The advertising arm of movie companies are definitely looking at the interaction rates of their trailer ads to help make decisions. The reason they do so is because it is a valuable signal.
> "Who really wants to click on an ad while in facebook on a phone?"
Advertising for apps (read: games) is a massive, massive market.
Most video ads I see are more informational than a call to action. Who really wants to click on an ad while in facebook on a phone?