Why isn't there a label for the tracking number in the order all complete email notification?/What does the "Service" setting in a non-integrated shipping method do?

If an order is shipped via a non-integrated shipping method, the order complete email notification will not display a "Tracking Number" label before the tracking number if the"Service" for the shipping method is set to:

 

If the service is set to:

 

then there will be a "Tracking Number" label before the tracking number.  The FedEx, UPS and USPS no integration options will also set the tracking number as a clickable link to the tracking information area on the carrier's website.

 

Note - The tracking number is entered on the shipment tab of the order in Pressero admin.  If you enter the tracking number before marking the order complete, then the tracking number is included in the order all complete email notification.