Strange Observation

So, my roommate A. lent me Clinical Microbiology Made Ridiculosly Simple for my microbio course. It includes these silly little drawings to help you remember the different bacteria and antibiotics. For tetracycline, they drew a solider (think "Tet Offensive"). His teeth are blackened, he is sunburned to denote dermatitis, he has shrapnel in organs harmed by the drug and a disease-carrying tick on his leg. All of this kind of makes sense...but....his fly is down.

I just don't understand why his fly is down. Is it to indicate that he is prone to venereal diseases? Some kind of commentary on the Vietnam war? (For the record, the solider is a Vietcong, rather than American solider). Bizarre artist license? I mean, it's not like your pen can slip, accidently drawing an open fly...someone went to some small trouble to draw all the zipper teeth in.

I wish I could include the picture, but I'm afraid I lack both a scanner and the motivation to haul the book into school to use their scanner.