Because it's easier to recruit at a Quaker convention than it is at a Republican gathering

Mike Stark is at the the US Conservative Political Action Conference and submitted a report with something very interesting in it:

Something else these folks have done well is turn out the new generation of wingnuts. The average age of the attendee here has got to be below 30 - there are literally thousands of College Republicans moving about in Brownian style from exhibit to exhibit, conference to conference, speaker to speaker, ballroom to ballroom. [...] There are no military recruiters here. No United States Marine Corps. No Army, no Navy, no Air Force or National Guard - hell, not even the Coast Guard is here. Thousands and thousands of College Republicans, but not a single recruiter in sight...

Mike has a theory which makes perfect sense.

If you're a military recruiter you have a quota to fill. Trying to get a College Republican into a uniform would be viewed by the commanding officers of recruiting units as an intentional waste of time.