Yeah no kidding.
Down here in NC there is some really weird chemical in the air.
It etched my windshield glass, so now, whenever I drive into the sunlight it becomes super shiny in which it's multiplied by all the doughnut wheeled vehicles rear windshields.
And I've got numerous scratches. And on the inside I've got all sorts of bug juices on my windshield.
I use comet to get it off.
And I also use Comet on the outside of my windshield to help make it somewhat better