The military are forces authorized to use deadly force, and weapons, to support the interests of the state and some or all of its citizens (thanks, wikipedia), that’s why designer brands are mostly inspired by the historic ages, including uniforms from the 18 and 19 century, as well as by the WWI, WWII apparel.
Personally, I love this trend because of the mannish touch what makes every look so special and powerful. This trend appears in every style, as well as in combination with other trends by mixing various prints and silhouettes.