It doesn't work with Commerce Kickstart because, Kickstart use a javascript widget to display quantity on the product page.

Comments

thanks @heyyo for reporting will try and look into it

Title:Compatibility with KickstartCompatibility with Commerce Kickstart 2

This is an Issue with the "Commerce Kickstart Product UI" module that comes with Kickstart 2.
This module adds a spinner JS and provides no configuration to control it, so it can not be turned off.
I don't think we can resolve it from our end as the two modules are modifying the same form element.
I will raise an Issue on kickstart but not sure if this is something they are willing to work on.
The only other option is for a user to disable the "Commerce Kickstart Product UI" module but this will disable all of the nice funky functionality on the product page.
optionally patching up the module by removing/commenting out the following lines

<?php
function commerce_kickstart_product_ui_form_alter(&$form, &$form_state, $form_id) {
  if (
strstr($form_id, 'commerce_cart_add_to_cart_form')) {
   
// Add quantity spinner widget & read more link
//    $form['#attached']['library'][] = array('commerce_kickstart_product_ui', 'jquery_expander');
//    $form['#attached']['library'][] = array('commerce_kickstart_product_ui', 'jquery_ui_spinner');
//    $form['#attached']['js'][] = drupal_get_path('module', 'commerce_kickstart_product_ui') . '/commerce_kickstart_product_ui.js';
?>

if anyone is interested can provide a patch