PARALLEL Hint ignored when there is a function used as a column in a SELECT statement

Hello,

I am playing around with the /*+ PARALLEL (AUTO) */ Hint in a select statement and it looks like this hint is ignored if there is a function used as a column in a select column.

example pseudo code:

 

select /*+ Parallel (auto)  */

e.employee_code,

  function.display_fullname fullname

from employees e;

versus:

select

e.employee_code,

  func.display_fullname fullname

from employees e;

Both these return same cost in explain plan.  however if you remove the function, it uses the hint and it is like noght and day.

select

e.employee_code

from employees e;

Why is this?  Can someone point me in the write direction to white papers or solutions?  I have functions that need to be used and can not be made into actual select statements as they are much too complex.