Recently Bhutan stopped free entry for Indian citizens.
What is the reason behind this action?
The newly introduced fee is called SDF (sustainable development fee). According to the foreign minister of Bhutan Mr. Lyonpo Tandi Dorji, this is done to regulate the tourist traffic. It will create a common tourism policy. Before this, the regional tourists needed additional permits to travel beyond certain areas. Also, Once implemented regional tourists would not have to pay the entry fees for many monuments & sites.
This is from a premier Bhutanese newspaper article. here