Except millions or billions of people use condoms, regularly.
The most drastic increases in AIDS does not come from the developed countries. The most drastic increases in AIDS comes from undeveloped or developing countries, where poverty is off the charts, survival is extremely low, famine is very prevalent, and clean drinking water is more important than a precious gem.
This is not because they're stupid or because they choose not to have unprotected sex (I suppose they do technically but...). It's because the education there is at such a low or nonexistent level most people in developed countries can't comprehend it. People who are in extreme poverty are much more likely to have sex/reproduce more, simply based off common facts...this is true worldwide. etc. etc.
In a place like Africa, the overwhelming majority of people who contract AIDS do not have access to care and medicine. They're also very falsely educated, if educated at all. The bare minimum of their education in the small villages, often times, comes from Catholic and other Christian missionaries who are blatantly spreading false information and actually inhibiting the use of condoms. They are, after all, led by an individual who has just recently maintained the stance that condoms can actually INCREASE the spread of STDs, including AIDS (the Pope if anybody didn't catch on). Yes, increases. Never mind the ~85%+ effectiveness at stopping the spread of STDs...yeah, they sure do increase the spread
Abstinence is the more legitimate, realistic method
There are many reasons outside of simple choice that determines who gets AIDS/HIV. Not to mention that there isn't a legitimate cure to AIDS, where as there is for the flu. If there is an outbreak of the flu, the public can be informed to get flu shots, to seek immediate care, and so on, and the spread can eventually be slowed drastically or stopped in developed countries. It's not that easy with AIDS/HIV. You either make someone be abstinent the rest of the life after contracting the disease (which is incredibly unrealistic and won't happen), you find a cure (also unlikely in the near future), or you find ways to prevent it...with condoms and other contraceptives, which many people are using.