A big reason why is that information is not enough. There are multiple 100B+ industries that are dedicated to driving sedentary and calorie-increasing activitie

A big reason why is that information is not enough. There are multiple 100B+ industries that are dedicated to driving sedentary and calorie-increasing activities (TV, gaming, fast food, soda, beer). There is far less effort devoted to getting people to exert more physical effort. Think about how the only real way most white collar workers exert ourselves is through "exercising". Aka moving around for the express purpose of burning calories.