Healthy people should buy health insurance or pay a fee for two reasons. One reason is that good health is not a given, even for those folks who keep their weight down and exercise. Accidents and unplanned illnesses happen.
Also, the expenses of those who become ill or injured and have no insurance are paid by you and me and other taxpayers when whatever savings they have are exhausted.
Another reason that all should buy health insurance or pay a fee is for the same reason that people with no children should pay taxes to support public education.
Our country works better if we have an educated population. An uneducated workforce drags down the entire country.
The country also works better if we have a healthy population.
For selfish reasons as well as unselfish ones, everybody should have health insurance–or pay a fee for not doing so.