Thought of another reason why there are many Indians on the forum but they refrain from posting in the Indian board. And I think it has to do with the Signature ... job? that they are doing.
Because the posts they make on local board is not counted towards the posts that pay, they don't see any reason to post here. They'd rather spend the time and effort to post somewhere on the forum where it pays.
This is another valid reason but there are good number of bitcoin signature campaign accept posts from local boards as well or atleast limited amount from the weekly quota so if there are Indians in certain campaigns can make use of it while gaining monetary gains.