I don't really keep up with this stuff, so I could be way off, but AFAIK the only countries that have the option of being paid actual money are the US, India, and Canada (and I think they only started letting Canadians do it very recently.) Everyone else gets gift cards. As far as being able to use those gift cards, idk. I would assume they would just use the Amazon sites for their own countries?
I don't think there was really ever any intent to make MTurk into something that people make an entire living from. There's still this widely-held belief, it seems, that this is just something that most people do for fun (and that might actually be true, idk.) But I'm sure there are plenty out there who think that being able to do a handful of surveys for Amazon gift cards is just fine, maybe even fun. Look at how many people use stuff like Swagbucks. They're not being paid in cash either.