Zombie Cliché Lookout:
I’m not speaking from personal experience here, but one imagines being around a number of rotting corpses would be an extremely unpleasant experience. Stumbling across a dead animal in the woods is generally more than enough decay for me; I can hardly imagine cruising around a town filled with bodies stacked like cord-wood. In zombie stories, however, characters are rarely bothered by this. Walking around streets liberally strewn with dessicated corpses must be something people adapt to quickly. When someone does make a fuss, they’re usually perceived as weak and/or feminine.
Of course, casually suggesting the group goes someplace slightly less revolting is just polite.