It would be so much better for efficiency and even for when you're on an airplane and a baby is crying if our ears worked like our eyes and we could close them at will. I could focus more on what I am doing when people are being noisy. It can even get distracting just hearing people move around in the library even if they're not being loud enough to be breaking any rules.
This change would ease a great deal of social tensions and help promote efficiency and make it easier for people to learn.
There are a multitude of reasons for why we blink, one of which being to help our eyesight stay useful. By blinking, we keep our eyes moist and we keep derby from damaging them. The same concept should work for hearing. Especially since we live in a world where we hear damaging levels of noise every day - jackhammers, car alarms, the neighbor playing his damn stereo - we need some protection.
There are plenty of real world medical problems that should be focused on, wasting money on changing human being's appearance at the genetic level is not one of them. Focus on curing cancers, and other disease that kill people. Buy ear muffs, ear plugs or use your hands, but don't waste money on that.