I don’t know about you but when I buy a new pair of sunglasses they always come with a case. It depends on the brand you buy as to what sort of case comes with them. A few times over the years I’ve been lucky enough to get zippered ones and I love them. They are useful for all sorts of things besides glasses.
They can be cosmetic purses, they fit brushes wonderfully.
You can put a few pencils and some note paper to keep little kids occupied when you go out to a restaurant or ….
They make handy cases for a basic first aid kit to pop in the car, travel bag or handbag.
They are just a handy little zippered bag that can be put in your handbag to take with you anywhere.
Don’t throw them out.