What maybe perplexes me more is why females don't (generally) tend to talk about the things you described above with your typical conversations with males. Is that a culturally flexible thing as well?

I'm not sure. It might be just my experiences with girls and my age. I'm only almost 23, so my close friendships with girls are from high school. In college I had 3 super best friends that were guys and never developed that same close relationship with any girls there. My close friends from high school are off living lives in their college towns, so I haven't really had a chance to really get close with them again. I wonder if our conversations would be different now that we're both older and have grown a lot since high school.

I might ask my mom what kinds of things she typically talks about with her close friends. It would be interesting to see if as you get older and the friendship lasts longer, the conversations shift. Based on overheard phone conversations over the years, I assume she mostly talks about their kids, how difficult teenagers are, and drama surrounding who is getting remarried and what their ex-wife thinks about that.

I know of guys who would really like to speak more openly about their personal lives (like me for instance)

I know for a fact you aren't alone there. A lot of guys have those same desires, but rarely admit to it or do anything to talk about it. If I'm hanging out with one of my guy friends, they do open up more emotionally, but there is still a large gap between what they actually are feeling, etc and what they chose to share and how they chose to share that information. A lot of time they downplay it a lot, even though I know they are hurting or really bothered by something. It's just different.

That has everything to do with evolution & society & cultural expectations. The male is supposed to fill the role as strong protector, and revealing anything that might detract from that is hard for them to do. I'm not sure how possible it is to change that. It is very engrained in our society and I suspect it will continue to be a trait passed down from generation to generation. Even as women become stronger and more independent and won't rely on men as much, I still think that gender role will be a prevalent part of society. Even now, it doesn't seem to be something to impress the ladies as much as it is something to impress or compete with other men.