Transgender individuals require hormone replacement therapy, they require psychiatric care during transition, and if they elect to get surgery it can take 2-4 years for them to recover to the point of being eligible to deploy. On top of that, after the surgery they are at a higher risk of infection for the rest of their life, which complicates any attempt at sending them to the field to train where hygiene isn't always able to be pristinely maintained or overseas. An overseas deployment also puts the individual at risk because they may not have steady access to their hormone replacement drugs, which leads to withdrawal and hormone imbalances as well as health problems. So, just like diabetics and cancer patients and individuals with physical or mental disabilities, it just isn't feasible to accommodate these people so that they can serve.