Many reasons.
Personally, I don't WANT to look female even if I was living entirely alone and never had to see another human being ever again.
I identified as neutrois for a while, but I've come to realise that I was trying to compromise in how I would ideally like to present myself to the world (certainly not saying this is the case for all who identify as neutrois - this was just my situation).
It's certainly not a traditional or uber-manly thing I'm going for - but I see a physical, base-body me that is distinctly masculine in form.
I'm currently planning on going on testosterone for at least 3-6months to lower my voice. It kills
me to hear my voice. I feel uncomfortable talking to my friends on the phone. It doesn't "pass" to my internal standards. It's not a voice I identify as my own and it's upsetting.
It's okay to be non-binary. But there's no wrong or right for anyone. Some people DO want to be clearly identified as male with no question - and there's nothing wrong with that. Some people don't, and that's okay too.