In a hurdle race, the point is to get to the end of the finish line first. Hitting a hurdle could slow you down or make you fall, so hurdlers try not to hit the hurdles, unless they're big beefy guys who can run through them without being phased. And you do see that. But generally speaking every hurdle you hit takes away a little bit of momentum so you try to skim the top, don't go high over them and waste energy, don't hit them and waste energy. They are heavy.
There is no "score" penalty for hitting the hurdle or knocking it over. Unless you intentionally do something unsportsmanlike, and that's a separate call. But if you accidently knock into it, even if it goes into the next lane and takes somebody out, you don't get a time deduction. There's no "points", this is not gymnastics, nobody cares about your style, this is track.