It seems to me that men have more need not only for sex, but for different women. It's not about sex, as in the process, but about different partners. Although this is very individual. People are different. It seems to me that this is from a certain statement that a man is of the "hunter" type. The more "booty" - the better. This is something from nature. :-))) Women are more reserved. Although not all. But in the bulk. :-))) One partner will suit them perfectly for sex. With which they will experiment there for themselves. It just seems to me that women are less in need of this constant change of partners. Even not so much because of moral norms, but in reality such a need does not arise. There is no instinct to "hunt" for everyone. :-))) Therefore, the woman found, calmed down, she has everything, but men often lack that very variety.
Like everything related to people, this can be explained by the laws of nature. Males aim to fertilize as many females as possible, to leave as many offspring as possible. Females aim to find one good male and raise offspring.
Why is this strategy entrenched to males? In most species, the male does not take part in raising the offspring. That is, he doesn't care, 1 child, 10 or 100, all the same, all the worries are on the mothers. In such conditions, the strategy of maximum fertilization is the most advantageous. Those males who have found one female and calmed down leave much less offspring than those who frantically rush through the fields, rushing at everything that moves. These "womanizers" pass on their genes and their sexual insatiability to a large number of children and this continues for millions of years.
Even now, when society seemingly encourages family values, restless womanizers find ways to widely spread their seeds, everyone can remember such a friend of theirs with 7 children from 3 marriages, while "monogamous" raise their two children and in the end always turn out to be losers in the cruel evolutionary race of "womanizers" and "monogamous"
Let's just say the question is too narrow (for me at least)! But I will answer!
Everything is much easier than it seems and the answer is in the question itself! If I formulate it differently, I think the author will understand why this is so!
"How to explain why men are looking for sex, and girls just wait until they find them, if sex is needed by both sexes equally?">
That's all! The society is built in such a way that men seek and seek, and women choose from the proposed options! And a man has to cast as many "rods" as possible to get sex, while a woman simply chooses from these "rods" ... This is the whole point and this is the whole horror of the situation.