I know from teaching that actors want to act. Even the subtlest actors can do a little too much.
I mean, the whole idea of movies was it was special to go to see - you went to a movie theater to see something that was magical and amazing, in a very special location.
But what's interesting is now - and not only in horror, but across the board - the studios basically only make B pictures with A budgets. That's the biggest difference.