I know. That bothers me too, to think that we'd have all these computers churning bitcoins instead of computing gene-folding and whatnot.

However, you could argue that mining for gold or diamonds is even worse. You ruin the land with strip mining, you get "conflict diamonds" responsible for a lot of human suffering and at the end of the day you just have more precious useless metal that you store in a vault.

That is part of the design: there is a point where trying to make a coin of X dollars costs more than X dollars electricity; thus, the money supply becomes constant. The value of the currency will then fluctuate based on the perceived wealth behind the currency.