jQuery on form submit works, but on form change does not

I just want to get this jQuery to work. When I do this it writes to the console just fine:

$('body').on('submit', 'form[action="/cart"]', function(event){
  console.log("I don't think this is getting here");
});

But when I do this it doesn't write to the console:

$('body').on('change', 'form[action="/cart"]', function(event){
  console.log("I don't think this is getting here");
});

my test website anyone can see is at http://test-4658.myshopify.com this script is on the cart. You can add and update stuff in the cart to verify.

EDIT: Some other ideas I've tried, with no luck:

$('form[action="/cart"] :input').click(function() {
  if($(this).closest('form[action="/cart"]').data('changed')) {
  console.log("I don't think this is getting here");
  }
});

And:

$('body').on('change', 'form[action="/cart"] :input', function(event){
  console.log("I don't think this is getting here");
});

Where did I go astray?