Here is a hypthesis:

HIV is only transmitted by getting it in the a.s.

Secondly, it can only be contracted by the RECEIVER, in the a.s (anal),
not the giver.

We acknowlege marginal paths to contraction such as needles, blood
transfusions, and occasionally through hetero sex (1 in a million?)

Hence, HIV spreads mostly among gay men and closet gay men and their
girlfriends/wifes, particularly in cultures where anal sex with women
is very common and/or closet gays make up a large percentage of gays

I think the least that could be done is to study this. But since this
hasn't happened yet to my knowledge, it indicates some strong lobbying
presence against any such research..