Its good when they have large crowds, but sometimes its nice to have smaller crowds. Every once in a while, I need to get away and not worry about being shoved and pushed around like with the large crowds. That's why I try to go during the week as much as I can.
Also with large crowds, there tends to be more teenagers and people who don't appreciate what the park is really about. During the week when its more older people, I don't have to worry about that.