Why do they say grown men don't cry?

I have a blessing and a curse...No I am not spider man, but what I am is emotional. Ever since I turned probably 12 years old I have gotten teary eyed at touching moments in movies/commercials/ youtube videos. It all started at a point in the movie Galaxy Quest with Tim Allen, Siguorney Weaver, and other no-name actors. Funny enough Dwight from the office has a cameo in that movie....but that is besides the point. The first time I watched that movie I was twelve years old in a hotel room in Southern California. At near the climax of the film Mathasar (The leader of the alien ship) is captured, and being tortured by the villain. Tim Allen is then forced to explain to Mathasar that the T.V. show that they were trying to recreate wasn't actually real. That they had been lying. Mathasar then let out a squeal that I can't describe with adequate words. Imagine a baby panda watching it's mother die a slow painful death, and that's the sound that Mathasar made. I couldn't help it....tears came flowing freely. Every since then I knew that I had a soft heart.

Many other instances have indicated to me that I'm just a big softy. A few others come to mind as I jog my memory. There was one time that I noticed someone had posted a touching video on someone else's wall on facebook. I took the liberty to watch the short youtube video myself. It consisted of various fathers reuniting with their families after their military service. The pure joy on these peoples' faces brought streaming tears to my eyes. Here I was, alone, in my apartment sobbing and laughing all at the same time. I was laughing at how ludicrous the situation was. Yes, I was a twenty one year old man crying my eyes out in my apartment. I have posted a link here so that you may all watch the beauty of the video, and somewhat realize why I was crying so much.

I have to add a the end of this post that it's not completely my fault that I wear my emotions on my sleeve. I am not completely sure if showing emotion is a genetically-inherited trait, but I would be willing to bet a buffalo nickle that it is. My father has always been a man of emotion whether it is crying at extreme makeover home edition, or crying during hallmark commercials. He has always let out a couple tears here and there. You know some people say that they've never seen their Dads cry, but it happens to me on a weekly basis. So that's why I pose the question why do they say grown men don't cry?