Checkbox's default value is CHECKED

The default value for checkboxes is 1, as set in packages/HTML/QuickForm/checkbox.php, however the CHECKED property is not also set. CiviCRM properly toggles the CHECKED property if the value is changed, but it isn't set on the initial value. I find it hard to believe that this problem really exists, so maybe I'm missing something. But the problem shows up for me, on the Drupal user register page, that the value for the checkbox is set to 1, but it's not CHECKED.