It's more than just a "social construct" It's imbedded in human dynamics.
It's the social dynamics between men and women. Men have to break past a girl's defenses to get in her pussy while a girl can have sex with almost any guy she wants AT ANY TIME she wants. Nothing is stopping her, there are a steady supply of men willing to fuck her.
On the other hand, men can go through pussy droughts, or be fully fledged virgins, which is extremely common. In my senior graduating class, at least half the girls had sex, while more than 90% of the guys were still virgins. Of course that changes in college when we have more chances to get girls drunk.....
But just observe the difference in how a male attains sex compared to how a female attains it. A man has to seduce and escalate while the ladies just have to open up their legs to the guy they are interested in.
Female virginity is a choice, Male virginity is a curse. In our society it compounds on itself increasing male insecurities.
Because of that concept, the girl will always be seen as more of a slut when she's having sex with multiple guys. Why? Because people inherently believe that she's overusing her right to fuck whatever human that walks on two legs and has a dick.
Its not just because they carry the responsibility of having babies. It's because men just can't get sex the way women do, unless you are rich and powerful.
You cannot tear this down. It will NEVER be torn down. If human life started all over again, this would be the same way, yet again. Girls would be seen as sluts if they have sex with alot of guys.