While, certainly not all those who claim to be the refugees might be actually one, the poor human rights record[1] of Bhutan speaks for itself. For a nation that issues citizenship based on race and origin [2] and "categorizes" them, a lot of economic development (and the self claimed Gross National Happiness) might be just a good publicity move by the Druk regime.

[1] https://www.amnestyusa.org/our-work/countries/asia-and-the-p... [2] http://thediplomat.com/2014/04/bhutans-human-rights-record-d...