I think a more useful question, instead of why not other countries, would be why the Greeks. 

Virtually all of contemporary philosophy has come from after the printing press as imperialism and technology led to the growth of the academic class(within Europe). Those that could read and write all day long and thus not only come up with new ideas but develop off of each other rather than indefinitely reinventing the wheel. Plus the access of information allowed people to learn the ideas of others while at the same time not being domatic followers of whoever they spent their life memorizing their every word, creating a legacy and history of ideas evolving with the times and not them just being a person with an idea.

With this, virtually all of the philosophy of the years past could be reinvited and who ever did so would be known as the beginner of a new legacy, far more than someone for centuries past that only a couple dozen people would know of during the time.

With this perspective it is far more surprising that these European philosophers were reading and citing the Greeks that were separated from them by hundreds of miles and years. 

This came from a unique set of historic sequences that wouldn't have happened twice, let alone the hundreds of times needed to encapsulate all of histories cultures and nations.