These doctors can treat a lot of different problems, saving time for the patient who otherwise might have to take multiple days off work seeing different specialists for each of their own and their family's medical problems. Managed care plans also cover many preventive services that traditional indemnity plans exclude. In the old days, people paid for these services themselves and the costs might not even apply towards their deductible. If you were a mother with three kids and lots of bills, you would not think twice about putting off your Pap smear, if seeing the doctor meant your kids could not get new shoes. Under managed care, there is no reason not to get that check up, since it is covered fully.
Some plans even eliminate the copayment for well care visits as an added incentive.
So, for a cancer patient or dialysis patient who does not qualify for Medicare or Medicaid, an HMO may be the only option. Also, there is no waiting period. Finally, do not discount the cost factor. Health insurance is very expensive. If a person or company can save money on an HMO, that may make the difference between being insured and being uninsured.