Not sure why this isn't automated. It caught me off guard a couple times when customers were emailing asking for tracking information, I thought something was wrong with the email notifications.
We ship a mix of from our store and drop ship, sometimes splitting orders to do so.
Not having an automated email sent to the customer when their drop shipped product ships doesn't make sense. We have to manually send an email with their tracking information, which takes time and effort that should all be automated.