Different data requires different access controls, and government agencies that collect / deal with a given piece of data on a regular basis are equipped to enforce those access controls.

You don't want your local dog catcher to be able to look at your medicare records just because "he's the government, and medicare records are government data".

> While Palantir is a private company and shouldn’t have access to government data, why shouldn’t in theory all government data be accessible to the government?

Shouldn't everybody have access to government data, with a few exceptions?

I feel like you answered much of your own questions.

Beyond that many of the departments that this data is being extracted from have rules about who can access (no not everyone in the IRS has free reign) and what they can do with it. For good reason, IRS's job is to focus on what the law says they should do, not say punish political enemies and so on.

But transfer it to DODGE, ICE, Palantir, there are no laws at all regarding what they can do with that data.

The problem is the laws - not the data sharing.

In some countries, tax data is available to everyone. Norway, Finland and Sweden in particular. There may be others

They're not just gathering IRS data. I'm not sure you read what I wrote at all.