Because Men Are Taller Than Women
Being tall and big gives the impression of authority. Women are not only shorter, but they tend to be curvier. In animations, the curves become very exaggerated and pronounced. It is possible to hide the curves by wearing a big coat during winter. Some women already hide their curves because of body modesty.
Because Men Have Deeper Voices Than Women
Having a deeper voice suggests authority and confidence.
Because Men Can Easily Make Gametes
Men can masturbate and spill the seed. Sperm is cheap.
Because Men Can Use Public Restrooms More Efficiently
Men can just go into the men's room and stand to use the urinals. There is no need to sit down in one of the bathroom stalls to urinate. Though, if men need to defecate, then they may place a toilet cover on the toilet seat.
Because Too Many Cultures Around The World Value Males
Many families around the world want a son. A son is an asset; a daughter is a liability. Raising a daughter in a patriarchal society essentially means investing in someone that will one day take a good chunk of the family wealth away to marry. If people are allowed to do whatever they want with their children, then, in a tough economic environment, daughters will probably be aborted, killed, or abandoned.
It may just be easier to be born with a penis. A penis is what people care about. As soon as a baby is born with a penis, the doctor or midwife assigns the male gender in the form of an exclamation, "It's a boy!" Then, the parents raise the child as a son and what it means to be a man. For some reason, parents never have a shred of thought of raising a biological female like a son, expecting male activities and going as far as using the male gender pronoun for the female son. Females have been made "kings" in history, but I suppose that's different than raising a kid. It would be an interesting experiment to raise a female like a son, but then it could also be a dangerous experiment. The kid may be scarred for life with parental-imposed gender identity issues.
Because Men Are Encouraged To Build Strong Muscles
Men are encouraged to build muscles and be athletic. That seems a lot healthier than encouraging women to become super-skinny, get a tan, and wear make-up that may be laden with toxins.
Because Men Are Encouraged To Play Sports
Playing sports increases physical activity levels and boosts overall health. That's better than standing next to the bathroom mirror and doing make-up.
Because Men Are Encouraged To Make Big Money
Making big money is perceived as a manly thing to do, even though meeting society's expectations of what would be classified as "big money" may be difficult, if not impossible. The downside is that men become workaholics and are less likely to become nurturing caregivers of their children. Meanwhile, women are expected to be the nurturing caregiver first and foremost, while work always comes second. Well, maybe the lesson for an ambitious professional woman is to not marry, or if one must marry, marrying a lesbian woman is more preferable than marrying a man, because a lesbian relationship is truly equal. Yep, I think more ambitious career women should enter asexual or demisexual homoromantic lesbian relationships.