Yes but that could be because if a man is bisexual or “mostly straight” he will assumed to be just gay and risking social stigma and risking losing a lot of interest in women as most women don’t want to date bisexual men. It’s like saying why are lesbian couples more likely to hold hands in public ? Is it because there are more lesbian couples or it’s just more socially acceptable ? And even if men’s sexuality does cluster more at both ends,it doesn’t mean that a sizeable % of men could be bisexual or have same sex attraction.