Until about 2013, I didn't use a case on any of my (Android) smart phones, and never broke the glass screen. I know I dropped them several times. The worst that

Until about 2013, I didn't use a case on any of my (Android) smart phones, and never broke the glass screen. I know I dropped them several times. The worst that would happen was the battery door would fly off. I started using a case when I got a phone that was thinner, and had a glued-in battery. I think having a removable battery actually makes phones tougher in a sense, because I the case of a drop there's an place for the force of impact to go without causing permanent damage.