Hyperstealth Biotechnologies did the research that led to the development of the Marine Corps camo, Canadian Camo, Jordanian Camo and many others. They use an extensive body of knowledge from diverse disciplines to develop sophisticated camouflage patterns.

Let's hear what they have to say about the Army pattern:
Designed for multiple environments ARPAT was derived from the U.S. Marines digital MARPAT, however one main difference with ARPAT was the removal of black in the pattern leaving it with three colors and with only one color scheme for Woodland, Desert, and Urban we believe it is equally ineffective in each environment, we affectionately refer to ARPAT as the Alternate Reality Pattern as we cannot determine on what scientific basis it was developed.
(Source)

As near as I can tell, the Army acquisition corps determined that all of Hyperstealth's experience and research wasn't as credible as the 'feeling' that black was unnecessary in the camo pattern.

The problem is that a pattern needs dark speckling to create the illusion of depth. Without the dark speckling, the colors will appear flat and stand out against the background (the complaint against the current pattern). Note that the discontinued six color "desert day pattern" (AKA "The Chocolate Chip Pattern") had this type of speckling, but was discontinued due to manufacturing costs.