No, you don’t. However, they are the best for two things: Safety and looks. Safety can help you if you have young kids around or are just a little clumsy, because no one likes to bang a body part on the sharp corners or edge of a desk. Rounded corners blunt the damage, and can also be more comfortable for your wrists. Finally, rounded edges, especially the waterfall rounded edge, can be very beautiful and nice looking if you are going for a more elegant themed desk. If you want something both cosmetic and safe then making sure that you have rounded rather than straight edges for your desk is a really good idea.