Newsflash: most people don't believe in BTC. This is a casino. If the volume of investment currently in BTC was made by people who believed in BTC, Mt. Gox wouldn't still be running the show.

It's allowed to continue because the volatility posed by such a shoddy and centralized exchange is precisely rollercoaster needed by the gamblers to play their hand. Everyone knows Mt. Gox is dirty, but they don't care because they are hoping to ride their coattails to quick profit.