Transmen need to be a lot more visible.
I feel like as an enby I benefit a lot from hiding under the "tomboy" label and a lot of transmen just pass more easily because while it's harder to create a penis through surgery, testosterone makes the rest of the immediately visible changes more easily vs estrogen can't change facial bone structure or un-deepen a voice.
There's also a society wide stigma not even necessarily about women but more about femininity. It's why you also see stigma against men expressing emotion and wearing clothing and engaging in hobbies that are traditionally "feminine." Often it's not even really women we have a problem with; it's the whole concept of femininity, no matter who it's applied to.
Both of these things make trans women a lot more visible in the public eye, but that also makes it easier for TERFs to act like this is a feminism issue. That would be (a little) harder if we were putting more transmen on the cover of GQ. Equality, y'know?