Not many dudes are into the whole post-op tranny thing; if they are, then they're another layer of fucking weird.
The appeal of MTFs in porn is because it's a "lady" with a cock. The audience catered to that niche is composed of aloof men who don't know that they're gay, and bi guys in the closet who want "Diet Cock," that is, the cock without the man behind it. In their eyes, if it's behind several layers of makeup and high heels then they can suspend their disbelief for five minutes until the post-nut clarity hits.
If there's no dick, then for the fapper, there's nobody there. Nobody to fap to. Time to move on.
There's even less of a niche for FTM porn because nobody wants a roided, hairy chick that has a bunch of masculine features. Even the butchiest butch to have ever lesbian'd has female characteristics that are very appealing. This is why there's a huge male audience for bodybuilder chicks but not for FTMs. One still performs femininity while having the roid clit and roid voice while at the peak of physical fitness, and for the femdom types, the thought of a big muscular woman throwing you around is hot. The other doesn't, and there's nothing that FTMs bring to the table besides "boy with a cunt." Whoopie. Just get a twink with a tight ass. You can't even be tossed around by them because most of them are doughy looking tards and the "fit" ones just look like 13 year-old boys who took tren.
EDIT: I'm actually going to edit this and add that another layer of appeal of troon porn is that women can't really replicate a cock a la futa. Shemales fulfill this specific need of weebery especially if they're HSTS's. Once the dick is gone the futa is lost and it's just a dude/chick (depending on who you ask) with a pussy. Probably another reason why MTFs are desired but FTMs aren't. A hole is a hole in porn, why get a Boy Lite when you can easily just get a twink with a "bussy." For a chick with a dick? Shemales.
