Some health insurance companies pay only 70%-80% of the medical cost incurred by their customers. What is the reason for this?

What will be an ideal response?

Medical insurance companies often do not pay the entire medical cost incurred by their customers. This is because if the insurers do not have to pay the entire amount of medical cost incurred by them, the customers are more likely to take better care of themselves because they have to bear a part of the medical cost in case of an illness.