What is driving the popularity of sedentary lifestyle?

What is driving the popularity of sedentary lifestyle? All it takes is a 30 minute walk, 5 days per week with stretching and few strength exercises 2-3 days per week, yet so very few get this balanced, holistic approach to fitness and health. What is driving this sedentary culture and why is it so hard for people to follow these basic guidelines? Why is not following these basic guidelines detrimental to health?