The reason why presidents can't keep their White House records dates back to Nixon

https://www.npr.org/2022/08/13/ [login to see] /trump-documents-history-national-archives-law-watergate
For the first two centuries of U.S. history, outgoing presidents simply took their documents with them when they left the White House. The materials were considered their personal property.

But for the past four decades, every presidential document — from notebook doodles to top-secret security plans — is supposed to go directly to the National Archives as the material is considered the property of the American people.

So when former President Donald Trump left office on Jan. 20, 2021, all his records should have traveled from the White House to the National Archives, according to Jason R. Baron, who served as director of litigation at the National Archives for 13 years.