Basically, Dalai just DOES NOT know how NOT to tell lies. He says anything convenient at the time. This happens to anyone who is picked up to do something he is not suited. It's a fault with the way he is chosen - the process used in his religion.
The westerners are not stupid enough to really believe him. They use him as a tool to extort something from China. Well, why not use such a tool when it's so handy and free.
For China, it's necessary to expose Dalai's lies as much as possible to the world to dispel the myth that created by the so called Nobel Peace Prize. Nobel Peace Prize is actually "Nobel Political Prize", which is a skunky stinky nonsense decided by the Norwegian parliament, and it does not have the same esteem as other Nobel Prizes.