Say you contract diabetes after your insurance policy kicks in. The policy may cover hospitalization during the policy term. With such covers and a lowered stress, the immediate danger of diabetes may go away.
But diabetes is a chronic illness. This means it comes back. And if it comes back before policy renewal, it could be considered a pre-existing illness. A lot of health-care policies do not cover pre-existing conditions. Therefore, you do not get diabetes coverage during your policy renewal. A diabetes-specific plan would account for the chronic nature of diabetes. It would continue giving you coverage or make the renewal policy easier.