Because those coins are all worth a million dollars each -- what fool would sell them for $700?
But BTC is trading for over $900 now... and plenty of people are paying.
What you do not understand is that Bitcoin is a new technology, that gives us capabilities that we never had before. Just like other powerful new technologies, it will slowly eat its way through every aspect of society until it has changed the world and everyone's life.
The same as happened with electricity, with the computer, with the Internet itself.
If you want to know where Bitcoin is going, take a look at the adoptions of other important technologies:
http://www.uversity.com/blog/wp-content/uploads/2011/07/Comm...