Because she lives for this, both figuratively and (since 2016) literally. Her husband past away several years ago. If she wants to keep doing it, good for her. She might be one of these people that gets bored easily and drives themselves crazy if they don't have something to work on. She probably doesn't have a hobby or other non-professional pursuit that engages her to the same level that being a Supreme Court Justice does.I don't get why these people want to continue to stay up there, go enjoy your retirement sheesh