It opens a few build options up for very long endurance missions. A completely reasonable example would be a large civilian survey vessel with an attachment of escort fighters. Sure if there is ever actually a fight it has to go home for repairs, it's not a mobile combat carrier, but until there is a fight that survey vessel can travel along without any maintenance concerns for it's military escorts.
It would also help in ways that wouldn't come up often in normal gameplay, but could in specific fluff settings, like Motherships or migrant civilizations. Currently the entire fleet has to set up shop on some asteroid every couple of years for overhauls, with non-repairing civilian hangars you would be able to travel without increasing the maintenance clock, but rolling back the clocks after battle, or repairing armor damage after battle, would require mooring and repair.
In real life even military maintenance facilities, like on an aircraft carrier, can only maintain normal wear and tear on their aircraft, repairing actual battle damage to the airframe is out of the question. I think that having civilian hangars that can repair battle damage would be overpowered and thematically out of place.