Because "patriarchy" only exists in the minds of feminists.
It is the female boogeyman.
Men are programmed to protect women. Its in our genetics and upbringing. So, naturally, men protect women from harsh sentences and other punishments. It is what men do, when we are figuratively in charge.
Not only do women get lighter sentences, they get easier, more luxurious accommodations. Some can even have their children come to visit them and stay the night.
Under matriarchy, all those signs "my body, my choice", they fall on deaf ears. Your body, our choice is the way of matriarchy. They will decide who can and who is fit to procreate. And the laws are much different. If you think women are emotional, just think about emotion based laws.
But hey, murder, when you were angered because you were wronged, totally fine.
And that is the correct answer..