Forget for a moment the Bible refers to Him as masculine (unless you have a femi-Nazi-approved Bible). I try not to argue gender about a spirit.
The reason Jesus was a man is obvious. You can't have PMS and remain without sin.
Yes, PMS, that reproduction-involved miracle of biochemistry that turns the kindest, gentlest creature into a sneering, snapping harpy willing to eviscerate anything that dares to enter her breathing space on those most unfortunate days.
"Moon days," the Indians call them. I can only assume it relates to the wackiness so associated with that celestial body that our word lunatic is derived from its name.
In season three of Buffy the Vampire Slayer, when Oz confesses to Willow he's a werewolf, she replies with "Well, three days out of the month, I'm not so fun to be around, either." Understatement of the century, Joss Whedon.
Leviticus says a woman is unclean during her monthly discharge and must go to the priests to offer sacrifices afterwards. You can bet money Moses was writing that little bit of wisdom in the back of the tent while Zipporah was on a rampage. Even God knows women are going to need extra grace afterwards.
The woman with an ounce of decency in her otherwise regular life will warn her fellows once she is aware of the chemical wash about to shut down her cerebellum and leave her reptile brain in control. Because the one thing you must never, ever do is ask "Are you PMS?"
How many tragedies could have been avoided by not asking that question? The world, alas, will never know.
God, in His infinite wisdom, side-stepped the entire issue by making Jesus a man and keeping Him single.
Because a man with a wife cannot be without sin, either.