For any of you that are still convinced that you need glass screen protectors on your iPhones, I have a challenge for you. Today, I proved to myself, beyond a doubt, that I have no need for glass, or any other types of screen protectors that are sold as useless money sucks. Today, at work, someone brought an iPhone 6 to us that had been dropped in salt water and therefore fried. Because the phone could not be wiped by software, we had to physically destroy the phone. Therefore, I decided to try something that I have never done before. I took one metal tool after another out of my bag and attempted to scratch the iPhone 6 glass. Screwdriver, pliers, sidecutters, etc, ALL failed to scratch the glass in any way no matter how hard I tried to do so. The tools simply slide off, leaving no marks whatsoever. Therefore, unless you are carrying some kind of tungsten-carbide bit or sandpaper in your pocket (I didn't have these in my tech toolkit), you simply are not going to scratch your iPhone glass.
So, try it yourself if you have an old, dead iPhone that you know is useless. You may just convince yourself to save some cash and skip the glass screen covers from now on.