Harvie, main reason is that in Latin and Eastern European countries, the idea of making even as little as 500 Euro / month is MOTIVATING!
For this reason there are a lot of professional micro stakes players from these countries. In Western countries with higher prices, higher standard of living, being a micro-pro is a lot less lucrative.
Becoming a poker pro is still relatively easy, but it's easier to do it, when you can pay all bills from the second month on. A western person will need to "suffer" a bit longer until they make enough to survive.
It's basic economics. Factories go to the cheapest country to produce your t-shirts and shoes because paying a Brit/German/French $15/hour with insurance, free holidays, and all of that stuff...well it's just not very competitive.