Simple: They want to shut down taxpayer funded research.

If they shut down public data access, you can bet the programs will be shut down soon after.

Ask yourself this: Do I, a US taxpayer, own everything the government buys with my money? Think I can take a trip to my local military base and use one of "my" tanks?

And before you counter that there is a difference between data/research papers and "real" things like tanks, the government (and the media industry, and the scientific industry, and...) don't see it that way. It is intellectual property, owned by the US government.

In the United States, works produced by the government that would be copyrightable if they originated in the private sector are public domain by law. Other than that information classified for national security purposes (let's not get sidetracked in a debate about the phenomenon of overclassification), the government's property interested is limited to real/tangible items.

Of course this doesn't mean people can just hack into the EPA servers, so to speak, but I would imagine it will not be very long before the administration is deluged in FOIA requests and is forced into making difficult choices about which information they will attempt to withhold from public scrutiny. If past experience is anything to go by, Congress will attempt to slow that process by continuing to underfund the judicial branch, but once the suits start to pile up you'll begin hearing the phrase 'writ of mandamus' a lot.

Edit: I left out the italicized bit about the government in the original which may have confused some readers. Sorry.

I get the point you're making, but the USDA's job is to publish documentation and guidelines for the food industry. If USDA wasn't capable of releasing documentation, it wouldn't have much of a purpose. The military doesn't have to interface with the public to justify its purpose.

The job of all government agencies is to execute the instructions given to them by the chief executives in a manner compliant with legislation enacted by congress. The agencies have no duty to the citizenry, as shown by a number of court cases where the government failed to provide necessary services, then argued they had no obligations (and won).

Devil's advocate: The public can still get the research data through a FOIA request.

Meta devil's advocate: you might be surprised how often an agency "can't find" or otherwise denies a FOIA request

Check out Government Accountability Office reports.

I like how the CIA says 'go fuck yourself' when they send back pages of completely blacked out text in response to FOIA requests.