Hi Levin: It’s quite a common point of view in religious contexts to worrying about to what extent can libido distract some men and women from a supposed true purpose. It’s also probable that social factors played a part. In ancient societies (and not so ancient), sexual and gender roles were clearly defined. Just as there were no female soldiers or women had no political rights, to vote or to run for office, in ancient Rome, they also didn’t take part in many other areas of life. Roles were clearly marked and as you mention, women had some private cults where men weren’t allowed either. The cult of Mithras, in that regard, was simply a male one. I remember that not so long ago, and probably still today, there were lots of institutions and conferrees in Europe that were exclusively male, and until quite recently nobody really thought of that as discriminatory, but of course, times have changed (maybe not in essence but definitely in form!)