Whenever somebody asks this question, I always keep the answer to myself because people think its selfish. But Ill tell you what I think anyways.......

Who gives a fuck. By the time we're dead, why does it matter. I say fuck it because thats the way life/evolution is. So why spend today, worrying about something that is inevitable? Do you really think that cars HAVE to run on gasoline? Hell no, but you wont see these gigantic oil companies donating money to fund research on another form of energy consumption. Human greed plays too big of a role today, to worry about tomorrow.