It is because it leads to far worse things! It destroys the habitat of animals, destroys the different species of animals and plants. It produces too much carbon dioxide and takes away the trees that are source of our oxygen that we inhale. If the trees are cut down, we will slowly die out of hunger because there will be no more animals and plants that will provide us food and our basic needs like clothes and many more. We will experience Global Warming and the Earth will get hotter that will result on the melting of the ice near the South and North poles. If these ice melt, the volume of water in the planet will greatly increase, if that happens, the mass of land will eventually perish, and our continents will get smaller and smaller. That means, habitat of animals and plants are destroyed and we will have no more food and eventually die!!!