StingingVelvet: If they did regional currency it it would surely be a one-to-one conversion, so you're saving money this way.
And that right there is probably why they aren't doing it.
When you use one currency, everybody can figure out sort of how much it's going to be, but when they're offering dozens of options, that means that they'd have to be changing the prices constantly in order to keep it at a 1:1 conversion.
There's also the issue of needing accounts to take all the various currencies they're accepting. Which is an added piece to keep track of as well.
cmdr_flashheart: I think I remember seeing screenshots of GOG with other currencies, has this been changed recently?
That was probably during the regional pricing scandal before they pulled back on it.