Good point, but it only takes one accident (i.e., Exxon Valdez) or one nut firing a couple of bullets into a pipeline, to make a really big mess.
No one ever comments about the pollution caused by WWII. Dozens if not hundreds of oil tankers were sunk from New Guinea to the English channel. Carriers went down. Planes went down. Every nasty chemical you can name was strewn across the planet. Two A-bombs were dropped. Yet things looked pretty good not that long after. Who cleaned it all up?