It's just slightly more complicated than that. :)

The main thing healthcare.gov does, which esurance and others don't, is to tell the user which government programs they're eligible for and what their subsidy will be. The law makes that calculation is actually surprisingly complex, for example:

  * there are at least eight different state- and federal-level healthcare programs (advanced premium tax credit, medicare, medicaid, children's health program, children's rehabilitative service, Tricare, VHA, IHS)
  * which programs you're qualified for depend on your state
  * the subsidy is based on which plans are available in your specific area and their cost, your household size, the ages of each person in your household, whether each person smokes, and whether you want a dental plan
  * for calculating subsidies, different sources of income are treated differently. E.g., tribal income for Native Americans is subject to different tax treatment, earned income is treated differently than capital gains in some cases, etc.
  * insurance is usually bought for a household, and there are precedence rules among different state/federal programs, so if any member of a household qualifies for a non-APTC assistance program, it affects the subsidy received for the whole household
  * to get the tax credit, your immigration status needs to be verified with the Department of Homeland Security and your income needs to be verified with the IRS. This is the work done by the "Data Services Hub."
  * by law, open enrollment starts in November but taxes are due the following April, so you can't compute the subsidy as part of the tax filing.

So you can see how something that seems like simple e-commerce task--buying health insurance--would turn out to be much more complex than a static site. You could argue that the law should be simplified, and I agree, but that would require an act of Congress and the cooperation of all 50 states. :) So, realistically, the software has to be complex to capture the complexity of the law.

(You could also argue that this complicated eligibility calculation should be exposed as an API, which would unlock innovation in the private sector. We want to do that, but need more help. :) )