Was watching some women's professional billiards and wondered why the competition isn't coed.
I suppose the most practical argument regards the break: men tend to be inherently stronger and therefore have an advantage on the break. But I'd be surprised if the data bears this out. Do men, on average, pocket a ball on the break more frequently than women in 9-ball?
Otherwise, the rest of the game is strategy, feel, focus, technique: talents I'd argue that aren't intrinsically better suited to either sex. If professional golf were only a putting competition, I can't see why men and women would have separate tours.
Maybe it's ego, insecurity. Guys just don't have the balls to risk losing to their better halves.