Ah but it does. Studies show that men are more likely to clicking on YouTube if they anticipate sexy women. Therefore the people at YouTube have allowed people it insert a “custom thumbnail” that may or may not relate to the video. What this does is increase the odds that one target group will click on the video. And it also is why the related videos will them go to women’s bottom.
The Sex Sells. And the technology is designed to use that sexy sex sex to get more clicks. Even funny videos like this, us the girl thumbnail trick. People click for the sexy girl but will stay for the funny.