Your choice to cover or not and nobody else's. But the first time it rains and you forget to close your vent and get water on the inside I bet you wish you had them.
(Cleaning out junk) I put a big nut over the mounting bolts maybe 1/4 inch thick, it's used as a spacer. And then put on mounting bolts. So I can clean out the neighbors tree out of them without taking them off. (Hate those trees) When they were mounted flush I had to take them off to clean, now I just wiggle out debris with ruler or stick. Includes frig vent also.