I think there is definitely a power component to uniforms. I’ll ignore the whole fetish thing for now—that’s a can of worms that I don’t really feel like opening.
Uniforms…actual uniforms that is, connote some sort of authority, official whatever, and therefore power. But that’s not what shows up most often in fashion. Fashion that’s based off uniforms also connotes some level of power too. Less than actual uniforms? More than actual uniforms? Dunno.
Is it a subconscious association with real uniforms that makes uniform-influenced fashion feel more powerful? Do brass buttons and epaulets make us subconsciously think of strong, authoritarian soldiers or policemen? Or is more general than that? Does the cut of military fashion inspire confidence and all that by itself? Uniforms tend to be more tailored and fitted; they conform to the body better…emphasizing strengths while maybe even concealing flaws. Is that it?
Maybe it’s back to the subconscious association with real uniforms. Military fashion tends to thrive in hard times. Maybe it’s because we want to wear military fashion to make ourselves feel stronger, more in charge, when a crappy economy or unpopular government is wearing away at all other control we have over our lives? (Maybe that's why the trend got so popular recently?)
Probably a combination of all that, actually. Should research further, if only to satisfy personal curiosity.