Answer :

The primary reason why the 2010 Affordable Care Act stands as one of the most important domestic policy plans in recent history is because it was the first of its kind. Universal healthcare had never existed in the United States before.

I believe the answer is: It provides health care coverage for millions of Americans.

The plan most commonly known as the ObamaCare. Currently, this plan is losing popularity since it required people to pay high payment for a specified insurance company (even higher compared to buy an insurance plan from a private insurance company). Even a large portion of democratic voters asked for it to be repelled.