You might as well ask "why do Japanese manga artists draw Europeans to look Japanese?" Swan has the typical shoujo 70s art with characters from Russia, England, the US*, Japan, etc. and I wouldn't be able to tell which character came from which country if they didn't tell me.

*There's a bit where the protagonist (Japanese) is in New York and is noticing that she had always thought that the US was very racially diverse, but everyone at the ballet school was white.