People learn by watching (it’s how we all learned our language, etc) and Josh said he learned so much watching DA take over the offense when he was hurt. When he came back he was greatly improved and he credited DA. Derek likely doesn’t want the grind of a coach, lower pay and enjoys the CBA restrictions. Another added factor is the number of years playing adds the the now rather lucrative NFL pension, something he’ll collect on long after his playing days are over.