Why is it unacceptable in western society to express emotions or share experiences you went through?

Try living in Ireland. As Freud once said: "the Irish are impervious to psycho analysis." and yes, I did steal that from the movie from "the departed" but the quote does exist. Feeling = Vulnerability. At least that's how it is over here, you let people know your feelings, you're easy prey. Closed off people tend to come across as stronger, even if they're completely broken on the inside. I wouldn't blame your parents though, they were probably treated the same way when they were younger. It's just a pity it was a trait that was passed one. Emotions can make you strong too, within reason of course. You just have to be aware of how to channel them correctly.