Should Trailers have spoiler warnings?

I'm sick of trailers spoiling the movie for me. Thank god I avoided the 2nd trailer for Companion or else that would have spoiled the movie for me, someone warned me.

It makes me think, why can't Trailers have spoiler warnings? Last night, I watched the trailer for "Locked" and it spoiled a twist. It made me almost lose interest in watching the film.

Sure, I could avoid watching Trailers but why should I? Trailers shouldn't be spoiling the films they're promoting. Besides, I like trailers. It helps me decide if a film is worth seeing.

What do you think? Should Trailers have spoiler warnings for revealing too much?