From the watch glass material, plastic glass does not appear that the old watch burst, and the mineral table glass, especially popular sapphire crystal glass is more prone to breakage.

As these films use less material they are cheaper to produce, not least because they can be deposited on bases like metal, glass and plastic.

One is to coat the glass with a substance that will make sure the glass doesn't shatter into pieces when it is broken--that could be a plastic material for example.