People tend to acclimate to smells with time and continual exposure, even the really bad ones.
Actually, if I'm not mistaken, the sense of smell can be so irrational at times and may vary a lot in intensity between one individual and another, so that you may smell something that stinks to the point he may feel tortured but another person right next to you may not notice and another may notice but be like "no big deal, it's not that bad"