It doesn't matter what sort of music it is, woodsie, the principle is the same. Sessions are set up by people to do whatever they set up the session for. That can include being a closed clique, if that's their idea of a good time. There ARE real reasons why some people want to restrict to certain genres and styles- it's even a bit surprising there's not more of it, given the pressures to adopt a commercialised, standardised, style that fits the marketing model. But that's an argument for another thread.

If that session isn't what you want, find another session that's a bit nearer the mark.