To the best of our knowledge Tibet has no oil reserves, or strategic minerals nor is in any way militarily strategically located in the eyes of the developed world.
Thats why the Americans have yet to make their foray into Tibet. This is why no one cares.
Sadly the Tibetians are aliens in their own land, with their cultural identity severely at risk. A generation or two from now,they will find place only in history books with a chapter, titled "A Lost and forgotten People"