I thinks the country that trade most of btc,is the european union and the united states,because if you find out mostly and exchange of bitcoin is dollar currency,they would not accept other kind of traditional currency as long you have change it to your own country.mostly american or european people want an recreation thats why instead they go to casino,they bet in online games,so in order  join the games they changes there  fiat dollar into bitcoins or other alternative coins to enter the online games.