I always thought of it as a hey-everyone-look-at-me kind of thing.
Ask Howard Dean why men don’t scream when excited.
Unless one is going for the rebel yell or the Tejano whoop, screaming in excitement tends to make a man look ridiculous. Not that the rebel yell or Tejano whoop won’t necessarily make you look ridiculous, mind you.
The Hollywood Scream: As a kid, the scream of one of the men on the tree bridge in the b/w version of King Kong haunted me.
I scream. Not some low-register hollow bellow either. I’ve screamed at movies, at pain, in pure furious anger… in frustration or fear.
Dunno. I think I’m a guy. Don’t think that screaming in head voice makes me less of a guy.
If a man screams like that, people will think he’s an '80s heavy metal singer 
At my last job, my [female] boss asked me about the male customers:
Boss: “Why do men always say ‘hello’? ‘Hello.’” (She pronounced “hello” with very clipped syllables.) “All these guys do that!” she said.
Me: Because men sound silly if they say, ‘Hiiiiiiiiiiiiiiiiiiii!’" (me going falsetto and really drawing out the “iiiiiiiii”, doing a pretty good impression of my boss…)
As to the shrieking, I try to avoid being in the same bar with a group of women celebrating one of their birthdays…
But I noticed this phenomenon way back when I was a little boy. I had been invited to a birthday party for a neighbor girl a bit younger than me. She opened one present, and it was a Baby Tenderlove™ doll, and she let out the most ear-splitting shriek you ever want to hear. Now, had I received something that I really really really wanted, I’d have said, “All right!” Not, “EEEEEEEEEEEEEEEEEEEEEEEE!”