I think, in addition to other reasons, is that people transitioning from FTM seem to be placed by society in consecutive boxes, each with their own type of invisibility.
Pre-transition guys are often seen as regular women, and are subject to a certain invisibility due to sexism. In addition, when you know you’re being seen as a woman, misogyny can make it hard to publicly force yourself to say something that will make you appear “unbalanced”, like “I’m really a man“, when you don’t yet look like one.
It’s not much more acceptable for a woman-appearing person to say that, than it is for a male-appearing person to claim to be a woman, especially considering that until recently very few people even knew trans men existed.
A “woman” claiming to really be a man might just be laughed at or dismissed, not even validated with the shock or horror a trans woman might receive, and he knows it. The health concerns of women and women-appearing people are routinely dismissed, and women-appearing people are often included in the female-socialization to not push back against that.
During transition, I think it takes a lot more effort for trans men to achieve “escape velocity” from their assigned gender than trans women need, because our society allows women to present masculinely. I don’t think we’ll ever decide for sure whether MTF or FTM people have a harder time passing as their correct gender, and I don’t think it’s a useful argument. But I do think it takes trans men more effort to “look trans” and begin their social fight, like they’ve got something going on, and are not just GNC women. Because of that, I think there are a lot more trans men trying to be visible than anyone realizes.
Once trans men can pass as cis men, I think they run headlong into that “shut up, straight man” thing which can be jarring to receive in spaces you’ve more or less safely inhabited all your life. Obviously some guys go stealth on purpose. But some guys just have a hard time figuring out how, or why, to ever talk about being trans. This can lead to their accidental invisibility.
I’m going to go out on a limb here and say that the abuses many trans guys have suffered growing up — which can run the gamut of all the evils traditionally done to women, with the additional trauma of being emasculated and having your identity gaslit almost out of existence — leave some trans men reticent to put themselves forward, talk much about themselves, or assert their perspectives.
Some trans men correctly see that you’ve still gotta be white, well-off, able-bodied, super fit, and conventionally masculine for the media to include you. And their social justice training might balk at the idea of conforming to that toxic definition of male value, just to win visibility.
Some of them are also deeply unnerved at the thought of becoming the type of arrogant egotistical men that talk over others, so they hang back, because our contentious socio-political climate doesn’t leave much middle ground.
And too often our struggles are pointlessly pitted against those of our trans sisters. In some social justice spaces, men are problematic, realizing you are one is regrettable, and wanting to be one is anathema. Penance comes in the form of taking a backseat, voluntarily or not. Whatever the actual circumstances of a trans man — including poverty, abuse or suicidality — it’s incorrectly assumed to be easier because he at least knows he’s a man, and therefore is immediately privileged. So it can be hard to access support from broader trans spaces.
If I were to be salty, most of why transgender men are “less obvious” is that we’re read as female, and society doesn’t listen to or give a crap about the unhappiness or medical problems of people who bear that label.
We’re encouraged to stop thinking about our own pain, wondering what is wrong with us, or pushing for relief–and go back to putting everyone else first, which is still the job of women and female-boxed people in every place that’s not an oasis of progressivism.
If you see a visible trans man, challenge yourself to accept him. Then you might see more.