Every animal has a personality. Every animal has it's funny little strange quirks. Some of them do these strange things just because they're jerks and wanna be annoying (not that that makes us love them any less), and some do it because of something that happened in their past that is still affecting their behavior now.
Such is the story of Harley - the famous tumblr rescue dog who was once abused and mistreated and now lives in her forever home and licks the mute button whenever the music on her human's computer gets more attention than her. She's lovely - happy as she is now and with every strange little quirk she has.