Final answer:
Mill posits that slavish adherence to social customs is detrimental because it undermines individual autonomy, hinders personal and societal growth, and prevents the learning opportunities that come from experiencing a diversity of lifestyles.
Step-by-step explanation:
John Stuart Mill articulated several reasons why individuals should not blindly follow customary practices set by others. First, Mill believed that individual autonomy was fundamental and that each person should have the liberty to make their own choices, as long as they do not harm others. This concept is encapsulated in Mill's harm principle, which asserts that the actions of individuals should only be limited to prevent harm to other individuals. Second, he contends that uncritically adhering to customs stifles personal growth and the improvement of society; without questioning and challenging societal norms, progress cannot occur. Lastly, Mill suggested that a diversity of practices and experiments in living are essential for discovering better ways of life. Essentially, if customs are followed without examination, society forfeits the opportunity to learn from the different experiences and ideas that are essential for human development.