It is outrageous that outsiders can't file complaints, since Congress has demonstrated its unwillingness to police its own conduct.
That's because there's an ethics truce. Both parties will deny this, but there is in fact a truce that's been in existence since 1998. And under the terms of the truce nobody will file a complaint against a member of the other party.
A man who lives in a $1.1 million mansion in Washington does not intend to move into an 814-square-foot cottage that he's rented out since 1997.