Trailer Talk: Why isn't anyone saying anything?

What the hell happened? There's empty bottles of eggnog and cans of beer piled knee deep in the kitchen. The rug smells like...ew. And I swear it tastes like someone had a party in my mouth and everyone threw up on the way out, then came back in and defecated in it. It was one hell of a holiday season.

As I groggily awoke and took in my surroundings, I noticed something on the TV. It was a trailer for a movie, but there was no dialog. No one seemed to be talking to each other. Just some dramatic music. What the crap is going on?

As I squint at the TV, a notion of an idea starts to germinate in my mind. Water, I need water. As I walk to the fridge, I freeze. Wait a minute, this is a foreign movie! That's why no one is talking! Americans are afraid of subtitles! Of course! It all makes sense!

For example, look at the trailer for, what was in my opinion, 2008's best foreign movie, Let the Right One In:



In this one, there are 3 lines spoken. In Swedish and subtitled. I wonder though, how effective a trailer like this is. If you're a person who hates foreign and subtitled movie, and you saw a trailer that didn't tell you the movie had subtitles, would you be upset when you saw the movie? For me, I like watching foreign movies, but I know not everyone else does. Am I the only one though who feels it's a little deceitful to make trailers like this? Or is there some other explanation for why studios do this?