Why are no NEGATORS defined in the standard operators

Hello,

while trying to bake my own fixedpoint datatype I noticed the definition for =(int8,int8) to be

CREATE OPERATOR =(

  PROCEDURE = int8eq,

  LEFTARG = int8,

  RIGHTARG = int8,

  COMMUTATOR = =,

  RESTRICT = eqsel,

  JOIN = eqjoinsel,

  HASHES,

  MERGES);

in PostgreSQL 9.5, but I wonder, why there is no NEGATOR clause defined here? According to the docs it should help to add

  NEGATOR = <>

In query optimization. Is there some reason for it? Or is it a Bug in pgAdmin III that the negator is not shown?

Regards,

Daniel Migowski