Just to clarify, not ONE single nation in the entire world, recognizes Tibetan independence. Not USA, not Russia, and not even India.
Not even the Dalai lama himself.
Dalai Lama: Tibet Wants Autonomy, Not Independence - TIME
Kashmir on the other hand, is internationally recognized as disputed territory, and is the subject of several UN resolutions.
Name me one single nation that recognizes all of Kashmir as belonging to India?
Give them the referendum you promised, oh mighty shining Indian democracy. Wait, what was that? The shining Indian democracy refuses to let the Kashmiri people vote in a referendum that they were promised?