It's just all part of a sense of fun...I'm not in the Secret Angel swap, but if I was, and you saw a postmark of Redmond, OR, it wouldn't be hard to guess who I was, by my location here.
By taking out my location, if someone doesn't know me well, then they might have a harder time guessing...
It's just a game, it's fun, kind of like knowing where everyone is from...what difference does it make?