Well, that and the fact that he was turned down for a student deferment to do graduate work in France (he'd already had four for college). If he didn't sign up, he would have been drafted into the Army, which was doing the heavy lifting in Vietnam at the time. So he enlisted in the Navy -- his bad luck that they decided to shift Navy troops to Vietnam.
Maybe Kerry will now support SCHOOL VOUCHERS for members of our military--
as a way to finally educate our men and women in uniform.