Because of the 5th Amendment. You can bet your ass that the DoJ will take your words and use them to charge you of a crime if you admit to it in front of Congress.
The real question is why was a man who was given a FULL PARDON by Sleepy Joe Biden allowed to plead the 5th? If you have a pardon you're already free from prosecution, so legally you have NO 5th Amendment right to stand on.
