Why doesn't the value in WC->session change?

Question

WooCommerce

I want to set a value to the WC session, I wrote a function:

function set_user_type_func()
{
  $temp = isset($_REQUEST['user_type']) ? $_REQUEST['user_type'] : '';
  if ($temp) {
    WC()->session->set('user_type', $temp);
  }
  die();
}
add_action('wp_ajax_set_user_type', 'set_user_type_func');
add_action('wp_ajax_nopriv_set_user_type', 'set_user_type_func');

However, the value in the session does not change.
At the same time, the correct values ​​are passed to the $temp variable.