If you are not self-employed in the US, typically your employer provides insurance coverage, most of which is pretty decent. If you are healthy, it doesn't really matter either way; unless you are involved in a serious accident or something, your interactions with the health system are infrequent and relatively simple.

I have, among other things, asthma. I'm a 1099 contractor; I buy my own health insurance. Prior to the ACA, which people keep threatening to revoke, I could not buy insurance that covered my asthma. I tried. I shopped around a lot. The same company that provided complete coverage at a previous employer had a pre-existing condition rider on the same policy.

After the ACA, my policy now covers my pre-existing condition (Yay!), but I'm paying $750 or so per month for it. If I could not afford $750/month, my options would be considerably narrowed. (And that's before the prescriptions for my pre-existing condition.)

Yes, I go in, I get treated. But my situation demands a pretty hefty bill anyway, or potentially a very large bill. Possibly enough to make me consider not going to get treatment.