Just, Why? ....oracle

I'm currently debugging a procedure of the form illustrated below, lovingly recreated using the ubiquitous scott.emp table. I'm also taking suggestions on what might've been going through the head of the person who wrote it.

RENAME emp TO emp_table
/
CREATE OR REPLACE VIEW emp
AS
  SELECT *
    FROM emp_table
/
CREATE OR REPLACE TRIGGER mod_emp
  INSTEAD OF UPDATE
  ON emp
  FOR EACH ROW
DECLARE
  new_emp                       emp_table%ROWTYPE;
  old_emp                       emp_table%ROWTYPE;
BEGIN
  new_emp.empno       := :NEW.empno;
  new_emp.ename       := :NEW.ename;
  new_emp.job         := :NEW.job;
  new_emp.mgr         := :NEW.mgr;
  new_emp.hiredate    := :NEW.hiredate;
  new_emp.sal         := :NEW.sal;
  new_emp.comm        := :NEW.comm;
  new_emp.deptno      := :NEW.deptno;
  old_emp.empno       := :OLD.empno;
  old_emp.ename       := :OLD.ename;
  old_emp.job         := :OLD.job;
  old_emp.mgr         := :OLD.mgr;
  old_emp.hiredate    := :OLD.hiredate;
  old_emp.sal         := :OLD.sal;
  old_emp.comm        := :OLD.comm;
  old_emp.deptno      := :OLD.deptno;
  update_emp (old_emp, new_emp);
END;
/

CREATE OR REPLACE PROCEDURE update_emp (
  old_emp                             emp_table%ROWTYPE
 ,new_emp                             emp_table%ROWTYPE
)
IS
BEGIN
  IF old_emp.empno != new_emp.empno
  THEN
     RETURN;   --can't update primary key attribute
  END IF;

  IF     old_emp.empno IS NOT NULL
     AND new_emp.empno IS NULL
  THEN
     DELETE FROM emp_table
           WHERE empno = old_emp.empno;

     RETURN;
  END IF;

  IF    (    old_emp.ename IS NULL
         AND new_emp.ename IS NOT NULL)
     OR (    old_emp.ename IS NOT NULL
         AND new_emp.ename != old_emp.ename)
  THEN
     UPDATE emp_table
        SET ename = new_emp.ename
      WHERE empno = old_emp.empno;
  END IF;
  -- ..
  -- ..
  -- ..
  IF    (    old_emp.deptno IS NULL
         AND new_emp.deptno IS NOT NULL)
     OR (    old_emp.deptno IS NOT NULL
         AND new_emp.deptno != old_emp.deptno)
  THEN
     UPDATE emp_table
        SET deptno = new_emp.deptno
      WHERE empno = old_emp.empno;
  END IF;
END;
/