Smell may be more closely linked to memory than the other senses, because the olfactory bulb and olfactory cortex (smell sensations are processed) are physically very close to the hippocampus and amygdala (which are involved in memory processes).
Thus, smells may be more quickly and more strongly associated with memories and their associated emotions than the other senses, and memories of a smell may persist for longer, even without constant re-consolidation.