The Kaiser Family Foundation released a poll Tuesday showing that public opinion is divided on the Affordable Care Act, also known as Obamacare. Forty-three percent of respondents reported that they approve of the health-care law, and 42 percent said they disapprove. That’s a marked improvement from much of the last year. But those of us who believe that the ACA is decent policy that’s working fairly well still need to ask: Why do its polling numbers remain so low?

At least part of the answer is that the ACA’s primary purpose was to cover people who had severe trouble affording insurance, and most Americans didn’t have this problem.

The ACA is at its core a coverage-expansion policy. It enlarged Medicaid and designed special marketplaces to give people who had limited or no access to private health coverage the ability to get quality insurance. That class of people included low-income Americans and uninsured or under-insured Americans with expensive preexisting conditions. Most people weren’t in those categories. According to polling numbers Gallup reported in January, the rate of uninsured peaked in 2013 at 18 percent, meaning 82 percent of Americans had coverage before the law fully phased in, and most got it in fairly stable “large group” plans, often from their employers, or in preexisting federal health-care programs.

Yes, the ACA has a variety of provisions meant to help people who had insurance before the law. It requires insurers to allow children to stay on their parents’ insurance plans until age 26. It is supposed to promote competition and price control among insurers in new, well-functioning health-care markets that can’t turn people away. Among other things, that will make people feel more comfortable buying insurance on their own, which enables them to leave jobs they kept merely for the health-care benefits. The law also requires a minimum level of quality among health-care plans, which helps some of the previously insured as well as the newly insured. Programs that punish preventable hospital re-admissions and promote better hospital care, meanwhile, are showing promise driving down medical mistakes.

But many of these benefits either aren’t clear to most Americans or aren’t associated with Obamacare in people’s minds. Fifty-six percent of Americans polled by Kaiser said the law has had no direct impact on them or their families. This number might change as the law phases in, but that’s where it stands now.

The ACA’s most spectacular success so far — and a primary reason the law is well worth its costs — is the plummeting rate of uninsured Americans. For the moment, that will have to stand as a moral victory, if not an obvious political one.

Update, 11:30 a.m.: Slight edits made above for clarity.