familiar scent is sextremely important to both wild and domestic animals. it's in their survival instinct to sniff out foreign or alien scent or scent that is new and poses a threat to their existence. for example, i don't wash the dog bed with detergent that puppy sleeps in. i dry clean it by slapping it 69 times under the sun and in the wind, and sprinkle some baking soda powder in spots where it smells really bad. he likes his bed with his dick and saliva stains. he will still lick his paws "clean" before napping even though i have already cleaned his face, ears, paws, dick and butthole with wet wipes.