How come no dangerous asteroid has hit earth?

We live for all these millions of years on this Planet and nothing dangerous has hit us in all this time and its kinda suspicious. We sometimes hear about dangerous Asteroids with a high possibility of hitting earth etc.. But nothing really ever happened. We are still here, unharmed, after all these years.

We are a rock rotating around a big object in the huge, empty, black universe and if you would look at earth from the moon, thats all you would think we are. And you would think that Something would eventually hit planet earth and damage it really badly, but we are still here.

Is something protecting us? Do we have an important purpose? Is something forbidding the human race from being harmed?

I don't know, this thought just popped up in my mind and i just wanted to Share it.

What do you guys think?