There are multiple scenario where restore is helpful

• In case user bought a subscription from say iPhone but the subscription is not visible on Apple TV, clicking on Restore button from My Account or My Purchase will enable subscription on the Apple TV.
• You have received subscription purchase confirmation from iTunes/Apple Store, but the subscription is still not active? Click on the Restore button from My Account or My Purchase and your subscription will be restored.
• You have deleted and reinstalled the app or restores the device from a backup? Simply click on Restore button from My account or My purchase and your subscription will be enabled.