Sharon Children, the disabled, and the extremely poor are covered by Medicaid. Not all doctors will take Medicaid patients so that can limit who they can see and which hospitals they can go to.
The elderly are covered by Medicare which most of them have paid into during their working lives.
The problem is people are who earn too much to qualify for Medicaid but don't have jobs where employers provide health insurance. This is why Obamacare is important. It provided tax credits each month that they could use to buy health insurance, and had good quality plans they could buy into with caps on what the insurance companies could charge for older people or those with pre-existing health conditions. Without Obamacare they were left with a choice of either no medical care at all - plenty of women were turning up at hospitals in labor having had no medical care in pregnancy - or selling houses to pay for care, or declaring bankruptcy. ERs have to stabilize patients even if they can't pay, so for a woman in labor that would mean delivering the child. She and the child would then be pushed out the door as soon as they legally could be.