Alan Lomax and colleagues did a comparative analysis of thousands of songs across the world's cultures. I'm not going to go into detail...or really explanation...but I liked this quotation about the project:
"And Lomax's overall conclusion, supported by very many correlations of this kind, is that 'song style symbolizes and reinforces certain important aspects of social structure in all cultures' (p. vii). If this seems at first sign a rather far-fetched and extravagant idea, then it is worth thinking a little more about what 'style' actually means in this context. Style is not the way someone chooses to sing but the way in which they sing without making any conscious choice; as Lomax puts it, 'if a culture member sings at all, he has to sing in the style of his people because it is the only style he knows. It is in fact almost impossible for anyone really to change his singing style. It takes years for a non-European to learn opera; it has required half a centruy for Europeans to learn to perform American jazz' (p. 28). At the same time style is something to which anybody who belongs to a given culture responds with precision: 'any culture member can immediately sense that something is stylisitcally wrong about a greeting, a cooking pot, a song, or a dance, without being able to explain why this is so (p. 12)." --A Guide to Musical Analysis, Nicholas Cook, pp. 200-201
So that's why I play everything like it's an Irish fiddle tune.