Yeah, I noticed the same when writing not-connected-to-anything flashfics.

I remember another writer saying they decided in one work to default to female and only make a character male if there was a reason (with a really low bar for "reason", such as "it makes this scene easier to write because the two people in it will use different pronouns"), and among the feedback was asking if it was set in a matriarchal dystopy, because all the men were gone. What does that say about the usual male-default fare we're offered...