A man in uniform is a man with status.
Depends on the uniform.
You're asking a question about women's tastes on a site for men? Might as well go on a woman's site and ask why men like boobs.
While agreeing with -- and laughing over -- Nick's post, I still think we can give some answer. A man in uniform is someone who takes significant physical risks. That is, he's brave. Bravery is an attractive quality. What's more, it's bravery with a point -- doing something good for others at risk to the self. And if he'll risk his life for society, he'll risk for her, as well. What's not to like?
So customs officers and airport security emanate braveness too?
But I guess I pitched this wrong.
What is it that triggers attraction from the uniform, is it a cultural construction of reverence or a personal ambition of providence? What elements do you think are in action behind aesthetics.
Postmen, milkmen, security guards? Maybe its a job thing. They're thinking that hey, this guy has a job so he has at least some money that he can spend on me.
Probably more of a "Dear Penthouse Forum" thing in those cases.
Because it imparts an air of order, authority, accomplishment, masculinity, strength and stability.
That, and also they look handsome in them.
As has been noted, you might have better luck asking a site with more women on it. Still, here are a few possibilities.
1. Many military uniforms enhance a man's appearance, emphasizing traits like the breadth of the shoulders while also providing panache.
2. Military men usually have to maintain standards of physical fitness above the average. Military forces also skew young.
3. A military uniform shows membership in a group that is esteemed by many, and that often is associated with manliness.
In short, I think that military uniforms and those who wear them hit various points of attraction, both cultural and primal, for many women.
Uniforms almost always fit and are almost always clean. They are hardly ever bad fads. And, like Nathanael says, the ones we're talking about are tailored (again, properly tailored). My guess is there's not much difference in women's reactions between a classic, well-tailored suit or tuxedo, assuming it's appropriate for the occasion, and the classic, well-tailored uniform. The problem is, uniforms are appropriate for more occasions than suits.