It's easier to sell a phone when there's not pieces of gravel embedded into the side. Cases are $5-10 and you can buy tons of them if you wanted the new case look. I've also never had a case that made it hard to fit in my pocket. My friend however did drop it in a parking lot and thanks to the raised lip around the front, the screen and corners were completely protected.
Yeah I will always buy a case even if its nothing but a cheap tpu case. Bu they make some nice slim cases that still do the job. After seeing reports in razr and razr maxx screens cracking when dropped I will not risk it. Having that material to cushion the blow goes along way as well as protect against keys, grime, and other foreign material.