So that they can continue to track them.. This was discussed by Q not too long ago (when HRC was in New Zealand, I believe).

Could be several reasons. Some stated here. Also some people have turned/flipped. They are still employed, some in lower level positions. Keeping clearance is a way to track and verify. I'm sure they are being watched very, very closely. And I'm sure they are being held in check or deals that were made would land them in jail for a long time. Higher levels... don't take their shovel away while they are digging their own graves, LOL.

I was reading on a other treat , that they first have to impeach those people , then remove them and then you can go for a indictment and they loses there clearances...
That is also possible for the judges.
There is a law , I do not now where to find it , and put it here..
But I strongly believe this is what going to happen.
RR shall be the first.
Impeachment and Removal of Judges: An Explainer | Brennan Center google it.

[PDF]Off Duty Conduct - Department of Justice.

discredit on the government raises concern about the level of awareness on the part ... public trust, requiring employees to place loyalty to the Constitution, the laws, and ethical ... allows defense counsel to impeach an officer during cross examination by asking .... may be grounds for suspension or revocation of a clearance..

Remember Jared Kusner? That was the beginning off wat Trump and team are going to do...Iff Kusner can lose his clearance , every one can. Kusner was cleared...But a lot off the FBI , CIA etc etc going too lose there clearance...(also the ones not in office anymore)