Why do cats knead?
Article gives two reasons: " 1. in the presence of someone with whom they feel safe ... because they associate the behavior of treading their paws with the comfort they felt when they were nursing2. It's possible kneading can be used to deposit scent... to mark territory."Some dogs like to suckle on your arm (or small squishy) well into their adulthood, so I suppose #1 makes sense.