cp --copy-contents questions

hi,guys
when i read the cp manual, found that have a --copy-contents option ,
in the manual it says :It is usually a mistake to use this option, as
it normally has undesirable effects on special files like FIFOs and
the ones typically found in the /dev directory. I wonder why should
remain this option since it always cause mistake just as the manual
says. which scenario should use it ?
thanks