Why do girls seem to get much more attached after intercourse than guys!?
I'll begin by saying that yes, there has been research on the chemicals that are released before during and after sex, and it has been found that women produce more of the hormone oxytocin during sex than men do.
Oxytocin is fondly known as the 'bonding hormone', because it's big in the game of the neuroanatomy of intimacy. It increases trust a little bit, and is involved in romantic attraction and possibly promotes fidelity in committed relationships. It's also the hormone that helps with baby-mummy bonding and all that shit.
So oxytocin is the standard response for this question.
But plasma oxytocin levels are also increased for men during sex, and the function that oxytocin plays in attachment after sex is not clear at all yet.
It's important to realise it's not a simple function of "Women release more of the 'bonding hormone' during sex and after orgasm, so they get more attached after sex". Oxytocin also causes spontaneous boners in rats, so let's not get too invested in it's role in romance.
In my opinion, the whole 'women getting more attached' thing, is mainly down to expectations. We have been sold this narrative so many times, that it's hard to not play along. And it's extremely difficult to untangle the web of societal norms and expectations in order to reveal true biological gender differences, especially within sex research.
But we do know there are plenty of women who are able to have casual sex and not end up with a bad case of the feelings. Just as we know there are plenty of men who fall in love with every woman they sleep with (actually, recent research has found that men tend to fall in love MORE often than women).
Because of the way you signed your name and your 'so unfair' analysis of the situation, I'm guessing you are probably a lady who is struggling with unwanted feelings of attachment after sex with men who don't seem to be feeling the same.
I think that for a lot of women, feelings of attachment are clung to after sex, because we don't know what else to cling to. Feeling good after sex is a good thing, and I think females tend to impress this good feeling on to their sexual partner rather than themselves.
Also to be fair, being penetrated is a little more dramatic than penetrating something, and can leave women feeling somewhat vulnerable, so it's natural to seek comfort from the nearest thing, which is usually attached to the thing that just penetrated you.
There are so many factors that influence feelings of attachment after sex, and YES it is avoidable. Just become conscious of the feelings that you are having and then question them. 'Am I just feeling this way because I just had a glorious orgasm and this person happened to be in the same room?' The answer is probably yes...
But also, remember, maybe you just don't like casual sex.