It does freaking hurt the environment, and so does burning the stuff we use. But think of the old ways mining worked. Underground mines posed a bigger threat. Especially to the miners in them, they can collapse on them. Whats worse is that underground mines that are dug out mountain shelves. If a mountain collapsed because a shelf way down below got too weak then you have one hell of a huge disaster.Now I'm not that grateful for this method but at least its more efficient.