[acdha]

Because researchers have been looking for those factors for a long time but haven't found anything significant. Yes, if you give people a pull-up test men will do better on average but there's a shortage of strong examples of more complex skills where there's a significant innate difference. This is especially true for professional skills where there are multiple paths to success relying on many different mental abilities, decreasing the odds that any single innate difference could be make or break.