To understand and answer this question, we have to rewind back to the point where you're able to see root cause why psychological types exist after all. It's irrelevant to ask why both men and women can be either T or F because it's just one of the possible effects how this plays out
Reason what makes us so hard to see answer to given question is that we mostly look at typology from the wrong perspective - perspective that describes effects not the cause and fools people into assumptions like typology is something that exists on its own or just to entertain us, without a real reason to exist.
Lets try to focus on cause instead of effects.
I believe everyone agrees we as humanity are here to survive. We don't know why we are here yet, but we're equipped with survival instinct - which is why we have primary need to stay alive as species, at any cost. Everything else on top of that is just an irrelevant noise that clouds understanding why different types exist at all.
Big mistake comes from default assumption like our planet itself is always static so we don't need to protect ourselves against it (but we do). That's extreme extravert assumption, as being cognitively extraverted makes you believe you necessarily see actual reality. That's not necessarily the case st all - but it'd be too long to explain it right here
So our planet can change (whole climate and other factors, it can be overflooded or hit by comet) same way like our inner world can change when we're ill and our perceptions get distorted.
How would we know to watch each others back in actual reality if we didn't have people on Se-Ni axis?
How would we know some genetic disease that would take us all down, threats us from inside if we didn't have people on Si -Ne axis ?
How to resolve issues which resolutions come from connecting ideas by reasoning on intellectual level and there were no T people left?
How to resolve issues which resolutions come from connecting ideas by interpersonal reasoning when no F people were left?
And so on.
Now it becomes rather obvious that having all the variability above present within our species, we can watch each others back from any angle in order to survive and rebuild Community even after harshest disaster. It's a really well thought through system by nature, as in the end nothing else matters except survival
Now we reach one level up and see that only thing that makes women and men really different, is that women can't get pregnant alone and men can't give birth to a child. Again, think of it on species level not on single person level.
I don't see any connection why ability to give birth and ability to fertilize should have any need to be properties of F and T. It's very common mistake in type forums that cognitive traits get associated with properties or effects that don't conclude from given cognitive function.
Think about it and it should be pretty clear
Homework for readers: what cognitive functions you guess to be responsible for coming to this explanation I composed on the fly? I'm a guy but would a girl of same type not come to exactly the same conclusion?
Additional question: what do you think, what's the reason types aren't present equally?
