Up until about 30 years ago, most people had traditional indemnity coverage. These days, it's often known as "fee-for-service." Indemnity plans are a bit like auto insurance: you pay a certain amount of your medical expenses up front in the form of a deductible and afterward the insurance company pays the majority of the bill.

Advances in modern medicine increased the cost of providing health care and made it possible for people to live longer. Those advances caused many insurance companies to look for ways to reduce their costs of doing business, giving managed care the boost it enjoys today.