Why do people just use the answer of the person before them?

I'm not a big contributer, but I enjoy Yahoo Answers. I have the feeling that for some persons, it is a very big part of their life and how they choose to spend their time. My question is why do so many persons simply use the answer of the first person who answered, or copy a great answer that the person just before them took the time to compose and many times research. I'm not talking about the case where one person has answered, and second person is composing their answer a few minutes later. Obviously, those are unaware of the other's posting. What I am talking about is maybe an hour later, or a day later, someone copies a previous person's answer. The reason I ask is because I've noticed who do this the most is top contributers. I know all of them don't do that, but it is astounding how many do. Why? Just to get more points?