This isn't unique to Balkan countries. It's much easier/more comforting to be with similar people in an unfamiliar place, especially if there are language difficulties. My grandmother came to the US as a teenager, a refugee from the Greek civil war, like many people in our area, and the Greek community was very strong: entire villages moved to the same city and lived in the same neighborhood together.

In the US, at least, there were two other factors: 1) Greeks (and in our case, also Albanians) hired each other for their businesses, especially in the wake of the civil war. A major bakery owned by a Greek immigrant family in our city hired basically anyone who came as a refugee from WW2 and the civil war, and diners were popular and largely owned by Greeks, and they hired their relatives and countrymen heavily as well. 2) Chain migration is a US immigration policy (and maybe elsewhere), where people can vouch for their relatives and make it easier for them to come to the country and naturalize. For decades my grandfather did this, hired the relatives (usually cousins) in his pizza shop, taught them the business, and once they were confident, they would open their own pizza shop in another town and bring over their families, and on and on. These people worked together, lived together (often the patriarch of a family would buy a "triple decker" apartment building and house the entire family in each of the 3 apartments, as they were built as cheap immigrant housing), and so formed their own insular communities that lasted a few generations.

All of this stuff is almost like a law of nature for immigrant communities, and you see it regardless of the community especially when there is a big language and cultural difference between old and new countries.