I am rough with my phones so I require some type of protection. They get knocked, dropped, ect. On my last phone I had a screen protector save my screen from my keys when I was helping unload a few 55gal drums from a pick-up. I stuffed my phone in my pocket hastily then grabbed onto the drum. Once it was over I pulled my phone out and it developed a large gash over the plastic. I peeled it off and the screen was perfect.
Fastforward to recently and a similar incident happened but no protector.
Phone is sporting a nice 1/4 gall from a key.
moral: Screen protectors work.