dbms_output.enable doesn't work ???

Well, it works as it supposed to be.
I was thinking that once I have dbms_output.enable, it would write or spool using dbms_output.put_line. But it did not.

Then came across http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:1968769482859

Which explains that we need to do:
set serveroutput on

to see output at sqlplus screen or spooled file.

Also explains purpose of dbms_output.enable.