What’s behind the Hollywood box office slump? No one knows, and don’t let anyone tell you they do, says Mick LaSalle. Yeah, the movies stink, but they always have, haven’t they? And yes, the ads and trailers are annoying, and the tickets cost too much, and c’mon, $8 for popcorn?!, but still… the fact remains, no one really knows what’s causing the slump, and it’s possible that, when the dust clears, it’ll just turn out to have been one of those unexplainable things that happens in the world sometimes. Or maybe not.