How much paperwork does it take to prove you meet those requirements and what is the cognitive/time cost of that paperwork?
Gentoo is free-as-in-speech, but way way too expensive for most people. Given that the US healthcare system is bewildering even to middle-class people who have relatives that work in healthcare, the cognitive costs of something like this might be considerable.
To tell the person asking "How does this works in the US?" That even if there theoretically are means to obtain the drug for the uninsured, it might be practically out-of-reach.