They don't all take them. You just made that up. The same case is being made with Biden. Special Council and all. What is selectively enforced?
You also forget that with Trump the National Archives and the DOJ spent a year trying to get the documents, were lied to and subpoenas ignored before they went to get them back. At least Biden and Pence disclosed that they had documents and have cooperated in every single way possible.
The Pence and Biden cases are almost identical. Trumps is an entirely different situation even though DOJ is treating them practically equal.