Well Glass coverage, as it is commonly called, comes with your comprehensive coverage.  Pretty common here in New York and to be honest, I have no idea why you would want to have comprehensive coverage and not glass coverage.  Really, it comes down to a math equation.  Average new windshield cost is $200+ mine just cost my insurance company $341.22.  My comprehensive coverage is about $100 a year.  Not a bad gig for me nor is it a bad idea for most people.  Honestly could be the best value in all of insurance, also the most used.  Goes right there with your Towing and Labor coverage.