Basically, the government takes way more information than it is entitled to already. And then doesn't secure it. Look up snowden leaks, opm breach, etc etc. Rereading the 4th Amendment might be helpful as background as well.

Lack of confidence in government and authority is my guess?

In case you didn't see the riots last week, many US people don't trust the police. If somebody knocks on your door, how do you know what their real motive is?

Are they there for contact tracing, to serve a warrant, to tip off ICE, or to plant something?

After all, the CIA used vaccines as a ruse to hunt Bin Laden.

I don't think police does contact tracing - usually it's the civil employees of the "hygiene office".