It's on file for a plethora of reasons. Most, if not all, repair centers have a track record of the services they provide. It's not only to have record of what and when was completed, but it also shows warranty history, repair status, updated owner information, notes made by the repair center, etc.
Look at it like a dealership when you have your vehicle serviced, they have every service documented on your vehicle and or owner information stored for obvious reasons.
It's odd your concerned over something service related out of your control with your Apple devices.