Ask Lemmy

Sorry for rant
There's a thing in sociology (or social psychology? I don't really know the difference) called "identity salience" that I think explains gender really well. Basically, people have any number of identities that describe them and they are of varying importance/salience. For example, it can be a big part of somebody's identity that they are a "father," but not a big part of their identity that they are a "driver" or "consumer." Maybe all those words can objectively be applied to this person, but he would likely identify strongly with one over the others. Similarly, right now I'm a "commenter" because I'm leaving a comment. That's something that objectively describes me, but I don't consider it to be an important part of my identity at all. Gender is just like any other identity; it's more or less important to different people. There's already a distinction between sex and gender, even colloquially to an increasing extent, and gender is widely understood to exist as a spectrum or multiple spectrums. It's reasonable to believe that people who don't consider a traditional gender to be an important part of their identity could consider themselves non-binary.
It's true that gender stereotypes exist, but there are plenty of positive characteristics that are also associated with gender like "men are confident" or "women are understanding." If somebody doesn't identify with any of those characteristics or even stereotypes, then they might just feel like they're not accurately described by gendered words. Of course, somebody who doesn't fit the stereotypical idea of a certain gender can still be of that gender; it's all subjective.
If you're interested in simple, objective, binary gender, it's called sex, not gender. And even sex isn't simple, objective, or binary when you really get detailed.