Because shooting, darts and snooker are "traditionally male sports". But from footbal to sprinting, the real physical difference isn't that big.
I dunno about that. The womens 100m record is 10.49 seconds, to put that in to perspective out of the 23 men that ran in the 2012 Olympics 100m semi finals the slowest time was 10.31 seconds. That means the fastest woman ever wouldn't have even been in the top 23 in the mens competition, let alone had a chance at a medal.
Go to more physical sports and I expect that difference would become even larger. Women couldn't hope to compete at the top level in sports such as Rugby or Boxing. Sure some women are far better at sport than some men could ever be, but when it comes to the highest level the men are just out of reach.