touchscreen - Is there a technical reason why most touch screens use glass rather than plastic?

Most modern touch screens in portable devices are made of glass.

This glass often breaks if accidentally dropped. Also, it is very reflective, making it difficult to use in strong light.

I know that touch screens without glass exist. For example, the multi-touch screen on my e-ink e-reader has a plastic front. I remember many other examples, such as the personal in-flight entertainment systems on many airplanes.

What are the reasons that most modern portable touch devices come with a glass panel on their fronts, rather than plastic or something else?

The cracking of glass seems to be a pretty big problem.

Edit: I've seen a lot of cracked touch devices, and it's nearly always only the front panel that's cracked. The actual display is usually fine underneath. Even the digitizer usually works perfectly.

Answer

When decisions about consumer electronics are made, many reasons beyond technical come into play. There is no valid reason for a phone to be disassembled in 7 pieces in order to replace a battery, yet that's how one of the most popular phones is made. Mobile phones are as much a product of marketing as they are of electronics, and many design decisions become clear when you take a look at that perspective.

Glass looks good, so it sell good. And when it shatters, people have to pay again - either for a new phone, or for a glass replacement job.

Plastic doesn't shatter or otherwise fall apart, unless you try to cut or burn it on purpose. It can also be made matte, which makes the screen much more readable in presence of reflections and glares. Since plastic doesn't have to be hard, it can be made thinner than glass, improving touch sensitivity.

Unfortunately, it looks cheap even before it is scratched (and plain terrible after), so you can't make big money selling phones with plastic screens. Worse, people will carry these cheap-looking phones for ages (because the screen won't shatter), projecting that cheap-looking and outdated image of your brand everywhere they go. So you either go out of business, or switch to glass like everyone else.