Non-binary just remains one of those things that seems a bit too much. Short hair and wearing pants doesn't exactly crush our concepts of gender norms for women. Like if you'd told me it mostly exists so people can go "gotcha" over someone using the wrong pronoun I'd believe you
it's also somewhat in opposition to trans-ness, but that end of the rhetorical spectrum can't acknowledge it
I still remember the tumblr movements of a few years ago when people were feeling out the limits and said stuff like "I was assigned male at birth but I'm transitioning to gastrogender"
like headmates, there was a collective unconscious agreement that this was too far
the whole idea of transitioning to the opposite gender means embracing all the common tropes (which as has been argued many times, still don't define the gender), but when there's no societal idea of the tropes associated with gastrogender, it's meaningless...much like non-binary