Same reason S Koreans aren't flooding luno - changing local fiat needs an exchange dealing in that local fiat. The SK exchanges offering 1 btc at +$4000 are the SK equivalent of luno - except they're dealing with massively more demand.
I'm sure banks can find a way around this, but I hear you.
Well that and you need to be a citizen of Singapore to trade on their BTC exchanges
I guess I better start applying for South Korean citizenship then