It doesn't go "back in the ground" though, does it? It gets scattered all over the ecology. When you take something that was buried deep and scatter it all over the surface - especially when that something is oil - that's usually considered an ecological disaster. Deepwater Horizon, the worst oil spill in history, has had catastrophic effects on the local wildlife, and it is still dwarfed in scale by the amount of plastic annually strewn to the four corners of the Earth.