The windows in your house keep the elements, such as rain and bugs, out. But the windshield in your car is part of your car's safety restraint system. In the event of air bags being deployed, the passenger side air bag in cars equipped with a passenger side air bag uses your windshield to deflect the air bag. If you had your windshield installed improperly, your windshield could pop out in the even of an air bag being deployed against your windshield.