biologically the primary function of your sperm is fertilize an egg to make a baby, thats what it does 'biologically'. you can't control biology (except w abortions and birth control pills and all other sinful and unnatural manner of things), but u can always make more sperm to fertilize more eggs. each moment u rub ur donger, think of all the unfertilized eggs in that same moment that u could have helped biologically that are going lonely w/o a sperm to complete them biologically, youre practically a murderer for not having at least 2 children by 2 different women each biological year imo
ppl also have recreational sex whose primary biological purpose is to reduce stress, same as in individual masturbation
maybe your confusion stems from the fact that sex as an act, has a purpose determined by the intentions of participants. sometimes, the intention is to satisfy the biological urge for stress reduction, in which case it should be called genital mutual masturbation or recreational sex, and that way we can tell the difference from the ppl engaging in the true reproductive sex for the purpose of conception that youre talking about.
now we can see that the purpose of sex is not always reproduction, but often stress reduction, so people shouldn't be punished with a consequence that they never intended. if the possibility of an abortion or the use of a condom allows ppl to control which biological imperative they are fulfilling, I for one welcome their freedom and don't believe in undoing women's rights to bodily autonomy in the name of an unscientific conception of an uncontrollable never changing biological destiny, or for the sake of some dubious claim that uncertain procreation potentials have the primacy to define all sex acts, or in the name of ensuring that sex always carries with it the risk of pregnancy out of some religious commitment to the sanctity of sex as a procreative act. I especially dont support this because science literally allows us to control that biology by using various procedures called abortions, that are based on scientific methods and findings and allows anyone who wants to have sex for a reason besides procreation to do so and thus to control their biology.