I've said this many times before, but virtual currencies have existed in South Korea as long as I remember. Crypto currencies are just the next evolution after Cyworld MiniLife was shutdown few years ago... Both South Korea and Vietnam are big markets for mobile gaming and all the extra features cost money. Not all mobile players are old enough to have own credit cards, so that is why they invented virtual currencies for purchasing in-game items. You can basically send virtual coins to anyone who has local mobile number.