You're right but it's still can be contracted if a woman is positive on her period (blood). This is why gay men contract it way more that heterosexual people because they do anal sex and there's a high change for skin ripping, plus they don't use condoms. Theres a reason why they're cautious about gay men doing blood donations.
My mom used to work in an STD clinic, and I have two family members that are nurses (one is an executive at a well know hospital network here in NYC). One of the issues in the healthcare community is trying to get gay men use condoms MORE
Saw a video on a YouTube page called jubilee with HIV positive ppl. One guy explained how he got it. "I wanted to be closer to a human and the condom was a barrier preventing that"
I always get my test done through my PMD, if hes on a vacation ill go to a public clinic (which is one in a blue moon). If you ever go to any public STD clincs in NYC especially the Chelsea clinic it usually filled with gay dude left and right

.
Bottomline, wear condoms.