Why isn't jQuery slide direction left working on show/hide?

Question

Can't figure it out why I cant apply 'slide', {direction: 'left'}, 1000 to hide/show in this case. If the slider is without 'slide', {direction: 'left'}, 1000 it works.

$(document).ready(function(){
    $('.custom-header__background>li:gt(0)').hide(); 
     setInterval(function() {
        $('.custom-header__background > li:first')
          .hide('slide', {direction: 'left'}, 1000)
          .next()
          .show('slide', {direction: 'left'}, 1000)
          .end()
          .appendTo('.custom-header__background');
      }, 2000);
   });