Speak Entry 5- Why is it that people sometimes "like us" more when they can get something out of us?

People sometimes like us more because they like to take advantage. They take advantage because they are probably either free- loaders or they just get into a habit of taking advantage of people. I don't really understand what it means when it says "when they can get more out of us," but my guess is that they take advantage. People might also do that because they might want to take advantage of becoming popular in a certain. In the book Speak, I don't think the Marthas are being good friends to Heather. I don't think they are because they are taking advantage of Heather. Since Heather got a job as a model, they are taking advantage of her because it's good for her to stay in the group and the Marthas are gaining popularity. This is why people sometimes take advantage of other people.