Is evolution cliché? Saliva has mild healing properties, and it's an instinctive animal response, including in humans, to lick wounds. Hence the phrase 'to lick one's wounds'. Of course, if you care deeply about someone, that instinct will extend to nurturing their wounds too. Ever had a cat? They'll lick your wounds as well, at least if they deem you a suitably fit servant. It seems like a really strange thing to get bothered over.