In the Seinfeld's episode The Contest, George's mother caught him masturbating. Later George telling this story to his friends.
GEORGE: So, she fell, and then she started screaming, "My back! My back!" So, I picked her up and took her to the hospital.
GEORGE: Her back went out. She's gotta be there for a couple of days. All she said on the way over in the car was, "Why, George, why?!".. I said, "Because it's there!"
What does it mean, because it's there?