Windshield chips happen naturally with driving. If your car windshield is chipped during a trip, you should get it repaired. Small rock-chips are considered wear and tear and are not covered by insurance.
If your car is returned with a cracked windshield as a result of a pre-existing chip or crack, it also may not be covered by insurance—so it's best to fix windshield issues before they worsen.
If your car is returned with a cracked windshield not attributable to a pre-existing issue, it will be covered by insurance.