Because men idolize women. Its one of the most consistent themes throughout history. Men grow up with this wonderful idea of women in their minds that will inevitably end up getting shattered by reality at some point, usually as his finally challenge for "growing up." So while we all lose that innocence of that beautiful image in our mind being real, we never forget how wonderful it was.

Given this, all those little faults and flaws get turned into beloved things. Look at the laundry list of things guy's can fetish about women. A fucking mole is considered so high on the list that they invented entire piercings just to emulate it.

Put these two together, and the female characters men create often end up being flawed enough to not be offputting but even more attractive while also being created with a love that you can often feel subconsciously.

Whereas when women are creating female characters they end up in two camps. The "idealized" version of herself. So either so wonderful that she becomes a Mary Sue or with her flaws so played up so they can be treated as good things that she becomes insufferable. The other is a character designed specifically to make people angry, either politically or sexually. This often overlaps with the "flaws played up but treated as a good thing."