I hadn't even considered slash fics (though I suppose they also qualify in terms of my initial question), I was mainly wondering because I'm mostly writing in fandoms that have metric helltons of invisible women who would almost certainly be somewhere in the vicinity unless the fic explicitly stated that the men were among themselves (gotta love all the erasure in Tolkien's world, really, but on the other hand it's a wonderful opportunity for fic-writing to try and fix things).

Your answer made things very clear, though - thank you. :)