In practice, in aggregate they are. As you mentioned, there were other countries filling that gap before, and there will be new ones. East Asia got there first because of a combination of factors (cultural, historic, and logistical), but once that area is spent, new frontiers will be opened. In fact, in markets where there are fewer logistical constraints (i.e. software), those new frontiers are already coming online (South America, Africa, etc).