This makes a lot of money for powerfully connected companies, so don't expect it to change anytime soon. This is why our congress and mass media treat Medicare For All as a joke or something to attack politicians on even though it's popular with a majority of Americans.
On top of this, my friends who work at (private, non-general) hospitals work a lot and are not paid what someone on HN might expect for what they put in. This isn't even necessarily ownership vs labor, since afaik the hospitals themselves are not usually in the best of places financially.
To me, the short version is: can't easily negotiate, information asymmetry, and captured regulators. Imo, this isn't helped that in USA we say "healthcare insurance" but what we mean/want seems to actually be "healthcare subsidy/guarantee".
[1] https://www.kff.org/medicare/issue-brief/whats-the-latest-on...