A hard case is supposed to protect your laptop. But there are certain low-quality material-made options out there that do bad instead of good. These are prone to make unnecessary scratches on the laptop body. You may also figure dent or scrap on the enclosure. Usually, the cheaply priced ones are made less effective to protect your laptop and rather cause harm to it. But then again. It’s not really a con of using a hard case, but actually a consequence of not buying the right one.