Mother Nature can be a cruel one. Being a mammal means we conform to the natures rules where the goal is to survive childhood, reproduce, nurture and protect the young and then die.
As I have shared, we have had dozens of cats, dogs, and horses. Being out in a rule area, and since we allow our animals to roam free "and" they respect the boundaries on average, we are decent providers.
But when we have spaded our animals they all follow a similar path. They get fat, are a bit mopey, and then bounce back. They live life, and then when it is "time". Most wander off away from the "pack" and die. We have had to bury a few.
But as you stated that is social expectations, what about sexual?
American society is still stuck in a puritanical sex is dirty and shameful mode. Therefore it is only assumed to be talked to for reproduction. Certainly we can look at it from a hierarchal setup of course (patriarchy), but if we look at modern western civilization in Europe where equality and feminism has really taken hold. We are seeing some interesting things. People are freer to have sex, but the invisibility factor is still there. Some could claim the ghost fingers of patriarchy reaching into the future etc. But conversely, there is another concern. Birth rates have fallen so low in some areas, now a reinforcement of sex for reproduction is starting to rear it's head.
One mighty presuppose that if people were society trained differently (e.g. women have equality and power and money at the same level as men have "and" men have the same level of power and money as before ... then maybe women who have sexual desires can go dip into the younger pool of men in a training sort of way to help educate younger men in being better sex partners and later better men in heterosexual settings.
But this would require a major restructuring of a lot of thoughts and people's actions.
Women can most certainly have children later in life and as they age. That is not in question; however, there are certain genetic and other energy issues that come into play. The older the eggs and sperm, the higher likeliness of genetic fault in the child, complications with birth, and during the "rearing" phase, adults have less energy if they have children at 44 and get them into college when a person is 62. Mortality happens.
So this was a rambling sort of response, but the first step is to ensure women and men that sex is for both pleasure of both genders "AND" reproduction. Also, that as a person matures, they ability to deliver pleasure goes up, especially with women.
For men the inverse can hold true if the only tools of the trade is his "you know what" ...