Huh what a coincidence I just watched this video https://www.youtube.com/watch?v=a_jjzzgLARQ which covers the trailer industry. Pretty eye opening to see all the tricks behind the trailers, a almost-must watch.
Sometimes you literally don't even need to watch the movie, you just got the tl;dw in the trailer.
I refuse to watch trailers for movies I might see, because they ruin the experience since I know everything that's coming.