If you have a blood borne disease, you should not be allowed in the military. The military is for highly fit personnel, who may be exposed to enemy fire, and therefore need to be able to provide and receive blood transfusions.
If you have a medical condition and you require maintenance drugs, you should not be in the military. You cannot then be assigned to positions where supplies could be interrupted during war, and you are taking up a position of someone else who does not have these liabilities.
Consider WWII in the Pacific as an example. There were plenty of personnel in the Pacific not in combat. However, every pound of supply needed to be used to support the war effort. Not maintenance drugs for someone rear echelon guy.
Correct. Both Type 1 and Type 2 diabetics are ineligible to join for exactly that reason.
Remember reading about a Marine boot who had allergic reaction to insects biting him. Was medically removed from service.
Almost unlike any other disease, HIV is a ticking time bomb, even if currently "under control." It only takes a couple of weeks for the virus to become detectable, and therefore transmittable, if current medications stop working or the individual contracts a different, drug-resistant strain.
If for no other reason, these individuals are absolutely disqualified as blood donors in the event of battlefield injuries.