The thing that is frightening about sharks is that they are perfect for their environment and we're inadequate in it to the point of helplessness.
I once met a guy who would travel to Nepal to take pictures of tigers. He said that tigers really weren't interested in eating humans because we just don't have that much meat on us. It's the same thing with sharks. Sharks use a lot of energy so they need to eat foods with a lot of oils or fat to burn (like fish or seals). Humans don't have a high amount of either. So we're not a good meal for them. Very rarely predators like tigers or sharks will go after people. But in those rogue cases, there's usually some kind of injury that prevents them from predating on their usual prey.
Sharks usually only attack people for pretty specific reasons; The human provoked them, they didn't know what the human was so they took a bite to figure it out, or they might see the human as a competing predator.