If you paid attention to the news during Operation Desert Storm, or a decade later during Operation Enduring Freedom or Operation Iraqi Freedom, you may have noticed an interesting peculiarity in the uniforms of the American personnel deployed therein. While the US military had possessed the forethought to design and produce camouflage fatigues intended for use in desert environments, they had neglected to do the same for load-bearing gear or body armor. This led to soldiers and marines being deployed in desert camouflage fatigues, with woodland or olive-drab flak jackets and load-bearing gear. The Army would address this problem by designing the Universal Camouflage Pattern, the now-discarded grey-light green-tan digital camouflage that dominated the 2000s. The US Marines would come up with a different solution.
While the Marines had switched to digital camouflage, they still had two different patterns, one suitable for woodland operations, and one for deserts. Rather than try to make load-bearing gear in both patterns, they settled on a color which wouldn't stand out in either environment. This khaki-like shade of brown would be designated as "coyote", and was used for the Marine Corps-issue Modular Tactical Vest, starting in 2006. The dark brown blends into most environments, and works with a large number of camouflage patterns currently in use. The adoption of Crye Multicam/Scorpion OCP by the US Army would do little to sway the rising popularity of this subdued color.
While camouflage patterns have proliferated in the decade since the appearance of coyote brown, it remains a popular choice for gear coloration. While the Naval Special Warfare community has had a fancy, exclusive camouflage pattern somewhere between the Marine desert and woodland patterns, they still use armor carriers in coyote. It has an added benefit for civilian users such as police or the unorganized militia, in that it's a non-threatening color. Black or camouflage would call to mind police or the more frightening militias of the 1990s, where brown has no such associations in the United States.
The proliferation of military-style equipment in the civilian shooting world of the United States has allowed the free market to make headway into the problem of camouflage development, but to date, most users seem happy to accept what the military has decided on. There's a certain aesthetic to the coyote-over-camouflage look, which many in the community have come to enjoy.