I often wonder the same then remember that I don't really care. I care a whole lot more about driving and getting the haul to the job on time. Whether or not other ETS2 female drivers are out there doesn't phase me. That said, I am a female driver. I choose not to disclose my gender via avatars or publicly (say on Twitch or Steam) due that I don't want to deal with drama. I just want to play my game (whether it's FPS or ETS2). I don't like drama, I don't want to stick out like a sore thumb, I just want to play my game. I've tried MP and decided not to get on TeamSpeak for the same reason. Again, I just want to enjoy my game without people shouting various stereotypes/stigmas at me.
Just putting in my 2 cents.