Repairing a crack or chip helps to keep the crack or chip from spreading.
It doesn't cover up your glass's defect. If you don't repair a crack, it will spread when glass increases in size in hot and cold temperatures, as well as when your car vibrates when it hits potholes or you listen to loud music. This is why, even though the damage is visible, it is critical to fill in these things.  For more information, visit the site.