There's a whole scientific explanation for this, and it has to do with making babies. Not every men's body decides to adhere to this rule -- men in their twenties may have horizontal boners whilst men in their sixties still point way up to the sky.
And, of course, if you're not quite fully erect at the moment, your cock may still point horizontally but not at the moon. Is a man with a "half mast" erection any less nice to look at than one with a raging hard-on? I'd argue not. After all, a man who has just had sex for two hours and cum four times may be at half mast before he plunges back in for more. (Thinking ideas like that causes me to get hard).
So here's to celebrating men at half mast. Some of these shots are much larger than they appear below, so be sure to click here to access a free folder with twelve photos of men at half salute, including all of the photos featured with this entry.