You know, people are doing all this to live longer.
Not really.
Eating a healthy nutritious diet is not about living longer. Medical science has no proof of that hypothesis. It is about improving the quality of life until you do eventually pass on.
For most people, there is a period of time when they have illness prior to death. For those who suffer from heart disease, diabetes, obesity, etc. that time period can be many years. This can cause both physical and financial hardship for both the individual and their loved ones. It also creates a burden on society in regards to the health care costs.
Consuming a nutritious diet, avoiding harmful foods and exercising can prevent or delay the onset of the chronic conditions mentioned above which can shorten the period of illness prior to death. This can provide many more years of enjoyable quality of life.
Many people feel that this is worthwhile goal.
Note: The above is a simplistic example. There are other mitigating factors such as genetics and environment; however, nutrition plays a major role.
? . . if you have to skip what you like? What's the point of living?
I certainly hope most people have a greater "point in living" beyond enjoying the taste of unhealthy foods.
You can eat anything you like, as much as you like, if you work it all off.
I pray that you did not teach your children this nonsense. I will try to make this as simple as possible. Exercise burns calories. It does not burn off any of the other molecules that you take in from harmful foods.
For example: The calories created from all of the ice cream and fatty foods you ate were burned off ; however, the excess of purines from these foods resulted in excess uric acid in your blood stream which could have eventually resulted in gout.
That is only one small random example among many that disproves your "eat anything you like, as much as you like, then burn it off" theory.