Rumor has it that it USED to be for determining which MOS's you could receive. That's why the Army Radio Score (or whatever the hell it's called) is on there. I think that there might still be some form of GCT requirements for certain enlisted MOS's, but I could just be talking out of my ass, which is known to happen from time to time. I'm pretty sure that it's just carryover from the days when enlisted folks not in possession of a high school diploma or a GED, though. We'd have to ask Brett to be sure, though.