Because you've got it backwards.
It should be, "Why do some men who don't want to go to men'ts prisons identify as women?"
And then, the answer is obvious.
No, Pearls. Red is saying, think about when the situation is reversed.
“Trans men” never want to be placed in men’s prisons, for the SAME reason biological women do not want “trans women” (biological men) placed in their prisons, restrooms, & dressing rooms.
It’s because “trans men” are biological women. They fear being raped.