We don't care about the things we get easily.
This is true in all the areas of life. Take health for example. Very few people take their health seriously. They know that if their health is lost, they won't be happy, still they eat junk food and never exercise, keep accumulating fat and keep spending on weight loss programs.
Still nothing works. Why? Because they don't take their health seriously and the real reason behind that is they have got it for free.
We spend thousands on cars and take care of them nicely.
Imagine what would have been the price of human body if we had to pay for it? And then imagine how well we would take care of it if we had paid a huge amount of money to get our body.
It can be extremely difficult to wean children off junk food.