Asteroids have us in our sight. The dinosaurs didn't have a space program, so they're not here to talk about this problem. We are, and we have the power to do something about it. I don't want to be the embarrassment of the galaxy, to have had the power to deflect an asteroid, and then not, and end up going extinct.
If you were to stand on an asteroid in the main belt of asteroids between Mars and Jupiter in our solar system, you might be able to see one or two asteroids in the sky, but they would be very far away and very, very small. So you wouldn't have this 'dodging through tons of rocks' business you get in the movies.