Why is continental crust generally much older that oceanic crust?

One aspect and way that I always learned was the sense the oceanic crust would be covered in non-stop water, this would then mean that to crust would be so fresh, it wouldn't have time for the sun and the wind, and the extreme rain to be poured on it for the crust to be ruined. But, as we talking about the continental crust, this would be the complete opposite of the oceanic. Therefore, we would then understand that they would practically live in different environments.

They use the si unit, or metric system its all the same thing