Paul Krugman in the New York Times, explains why Hillary’s healthcare plan is necessary

And it’s not just a matter of principle. As a practical matter, letting people opt out if they don’t feel like buying insurance would make insurance substantially more expensive for everyone else.

Here’s why: under the Obama plan, as it now stands, healthy people could choose not to buy insurance — then sign up for it if they developed health problems later. Insurance companies couldn’t turn them away, because Mr. Obama’s plan, like those of his rivals, requires that insurers offer the same policy to everyone. As a result, people who did the right thing and bought insurance when they were healthy would end up subsidizing those who didn’t sign up for insurance until or unless they needed medical care.