[GENERAL] Why are no NEGATORS defined in the standard operators

[Daniel Migowski]

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