They’re not manda­tory in Eng­lish. But as a side ef­fect, Open­Type lay­out fea­tures have al­lowed type de­sign­ers to add lux­u­ries to their fonts—like al­ter­nate fig­uressmall capslig­a­turesor­di­nals, and frac­tions—that had pre­vi­ously been dif­fi­cult or im­pos­si­ble. That’s the good news.