The bottom line is, prisons have to prevent rape within their walls. If a victim contracts AIDS because of a prison rape, that's a lawsuit and a potentially grand settlement.
Considering that prison rape has gone on for decades and AIDS has also been going on for decades, it's a certainty that some poor bastard already got this death sentence. So far, no successful suits and no large settlements.
In short, ain't nothin' gonna change any time soon.