Women bear the risks and the costs (e.g. metabolic costs) of pregnancy. Men don’t.
From a reproductive standpoint, a man has a simple problem: How to get his sperm into as many uteruses as possible.
A woman has a complicated problem: How to get desirable sperm into her uterus, while avoiding getting undesirable sperm into her uterus.
It’s crucial that there’s no evolutionary distinction between your dying and otherwise failing to reproduce. Evolution doesn’t care at all whether you die at age 5 with no offspring or die at age 105 with no offspring. These are the same outcome from an evolutionary perspective. Not approximately or metaphorically the same, literally exactly the same.
In the evolutionary past, a woman could die in childbirth, so having sex meant she was non-trivially risking death. On the other hand, never having sex also meant that she would die, from evolution’s point of view.
So sex is fundamentally more complicated for a female. It is both desirable and undesirable, lethally fearsome and irresistibly attractive. This is why female behavior, especially female sexual behavior, is so psychotic.
Imagine that you were locked in a room full of hamburgers and were not going to be let out for a month. Imagine also that you knew that a significant proportion of those hamburgers were poisoned and would kill you. To avoid starving to death you have to eat. That’s an inescapable, rock-hard given. But also, to avoid being poisoned to death, you have to avoid the poisoned hamburgers. That’s also an inescapable, rock-hard given. Imagine what your behavior would be like in this situation. Now compare it to actual real-world female sexual behavior.
Furthermore, while it’s female reproductive (and therefore sexual) behavior that is erratic and psychotic, this is potentially everything, which is why their behavior in general is so erratic and psychotic.