I think the reason I don't use statistics more often is the difficulty of getting good data sets; and even when there is good data, there are often ethical problems with following it. For example: Bob lives in America, and is seeking to maximize his happiness. Americans who report high levels of spiritual conviction are twice as likely to report being "very happy" than the least religious. Should he become a devout Christian? There's evidence that the happiness comes from holding the majority opinion; should he then strive to believe whatever the polls say is the most common belief in his area?

Another example: Bob has three kids; he knows his wife is cheating on him, but he also knows the effect size of divorce on child outcomes (depression, grades, income, stability of future relationships, etc.) is larger than smoking on lung cancer, aspirin on heart attacks, or cyclosporine on organ transplants. When do the bad effects of staying in the marriage outweigh the bad effects of splitting up?