In the end it is all about numbers and quality.
When the insurgency in Iraq heated up, a large amount of Soldiers were not reenlisting and civilians were not real excited about joining. In an effort to fill the ranks, the Army began to allow people with GED and other things like felonies that once barred people from joining the Army. However, lowering the standards for the Army brought in a higher amount of people who were more of a problem then what they were worth (ie drug dealers). Now that the economy is better, the standards have gotten higher.
The days of recruiting from prisons and the scum of society are well behind us (referencing British history).
"The best form of taking care of troops is first-class training, for this saves unnecessary casualties." Erwin Rommel