Tiger Woods wins on 19th hole sudden death -- why is sudden death fair after not using it before?

I will post more final thoughts later. Here's something to think about: The U.S. Open has an 18-hole playoff system that converts over to sudden death playoff. Why is that system fair? If you think 18 holes is the better, truer test, you shouldn't switch over to sudden death ever. Might go another 9 holes, or another 4 holes or 3 holes, but the switch to sudden death brings right back into play the whole notion that sudden death doesn't really produce the true test of the better golfer -- one bad hole and you're toast. The sudden death killed Rocco's chances, in a way. One bad drive and he's toast. In my book, unfair if you actually buy into the whole 18 hole playoff system (which I'm not sure I do).