"Why are straight men not emotionally open"
Because almost all of us have a scar from when we trusted we could be and it killed our relationship, or was used against us, or provoked disgust or suspicion. And I don't mean from other men.
The problem here is that patriarchy has dug itself so deep that lots of folks believe that men basically need to be tough dudes without feelings, who don't cry, who never shed a tear. So when dudes inevitably break down at some point in their life and try to reach out to someone, only to then have it shoved back in their face, it's not the fault of the person who has internalized the patriarchy but rather patriarchy itself. It is patriarchy that decided men shouldn't have feelings, that we should idolize war heroes, John Wayne, stoics, deaden our emotions, and basically be sacrificial fathers who are there simply to provide and protect.
The world has changed, however, and now we've run into a situation where the qualities that were valuable in the past (which again were always self imposed by men) are no longer necessary or in fashion. So the patriarchy is like a snake eating its own tail in that those who are victims to it begin to think it's the only way and that's how it just is -- so it's no wonder that women who are victims to the patriarchy, internalize it to the point where if they are to survive in it then the men need to hold up their side of the bargain too and be the robots they said they wanted to be and should be.
The patriarchy hurts everyone, not just women. It's why movies like Barbie are important cause it went to show how the Kens were wanting simply to gain each other's respect by winning Barbie's attention. They could simply forego Barbie as an object and device for their own fulfillment by just talking about different ways to fulfill their competition or accomplishments. But you know... patriarchy... using women as trophies to self-define their success.
It then is tough when you are a man who can talk about emotions but women aren't used to it, so they may listen but just have no solutions for them because they haven't lived that experience. And those dudes have trouble finding other men who are open to talk and relate. So again, not the problem of the women. So it's no wonder that the men just stop looking to talk or for help in feeling their emotions. But that's why we need more open discussions and allow men to be full human beings and not just rigid binary creatures.
Little rambly there but hope the point came across.