I can smell the living too, but that doesn't mean I can smell a living person hiding under a bed. Zombies don't have superhuman senses, their senses are no greater than the living counterparts. They don't hunt by scent, they hunt by sight and sound, and if you are close enough standing by them that they can smell you not rotting, then you've got a problem.
Uhhh... except in season 1 they had to cover themselves with rotting zombie to not be noticed and the second it started getting washed off, they realized they were humans. Bad continuity if you ask me...