It has been shown that prehistoric peoples throughout the world danced in lines and circles in the same "W-hold" position that is used today for much of Balkan dancing. There are many reasons why people outside of the Balkan region love the Balkan dances in particular: the haunting music and rhythms, the unified feeling one gets joined with others in a line, for two reasons. Perhaps the difficult struggles that have fraught the region almost continuously since the Stone Age have made each village reinforce its community in such a strong way.
One thing is clear: You can't really experience this dancing by watching. Like most of the other activities on this site, it is participatory and you have to give it a try!
For a learned breakdown of why line and circle dance are important to people's feeling of community and well-being, read Barbara Ehrenreich's Dancing in the Streets.