I was asked the same thing by the professor who I had to see to get a referral to a gender clinic. It's policy if you have a diagnosis. Found out later that this clown had been instrumental in creating trans care policy in this country.
He suggested that the reason for me "thinking I was trans" was that I couldn't handle being gay and had to become a woman to legitimize being with men. Transitioning obviously being the easier option since us trans girls are so universally loved and respected.
In the second meeting we had I pointed to my genitals and said that these have to go. Dude looked super annoyed but that was it, the meeting was over and I got my referral.
I get that it could be a valid reason, but I had already told him that I had been with guys but the dynamic was all wrong. The problem I have with sex in general is that I do not want to use my factory installed equipment as intended or at all, preferably. That's why my ex wife kicked me out. I just couldn't give her what she needed anymore. I told him all this, but he still said that I should gay it up more first. I had also told him that gay porn does nothing for me as there's no one to identify with. That's a big reason why I convinced myself I wasn't gay but the attraction to guys were still there. I couldn't get my head around why that was. Until I realized at the tender age of 55 that I'm actually a woman, of course. Being trans was just not on the map for me as I barely even knew that existed for most of my life.
He is quite known in the trans community as not being trans friendly and having outdated opinions.