We have noses to breathe smell and taste. The structure of our noses is the way it is because we are warm blooded. The conchae of the upper nasal passages permits the warming of air and id is found in all warm blooded creatures. It was in fact by identifying nasal conchae in the fossils of some dinosaurs that scientists were able to determine that some dinosaurs were warm blooded.
So we can smell, I don't know why everyone is saying their good for breathing, I breathe through my mouth because my nose doesn't give me enough air, also I do a freakin face palm when people get a stuffed up nose and say they can't breathe, breathe through your mouth people! it's not that hard when your nose is stuffed up!
They are desgned for smelling. Smelling tells us valuable information about our surroundings. If you smell smoke you know there's fire and hence potential danger. When you see an unknown food you've never tried before and you're trying to make up your mind whether you want to put it in your mouth what's the first thing you do? Smell it. Or if you don't know if the milk in the carton is still good. When you smell you inhale tiny airborn particles. Your brain interprets them, identifies them, and categorizes them as good or bad.