I know that is the perception, but Jokic absolutely cares. He was crying tears of joy when the Denver championship banner was being raised. Look at his celebrations when he hit that half court game winner against Golden State or when Jamal Murray hit that game winner in the playoffs against the Lakers. He doesn't turn himself from a fat slob into the in-shape player that he is now and arguably the best player in the world right now if he didn't care. You can also look at his workouts with the rest of the Nuggets-they do some serious uphill running at altitude.
The things that Nikola does not care for are the press conferences or the peripheral things he has to do when playing.