Is for the living things on it. Water isn’t rare, you can find them on asteroids. Minerals are also very plentiful in the universe, and aren’t worth traversing the vast distances of space to acquire. The only thing that seems to be relatively special about earth is the fact that it has life on it. Life seems, to be very uncommon, at least advanced life. Any advanced alien civilization is more likely to be interested in our philosophy, biology and or culture then our resources(save for maybe the life sustaining planet we live on). What do you think.