He's not retiring. He's taking senior status. Same pay, less work. More importantly, it opens a judicial vacancy for Biden to fill. For the first time in generations the control of the courts by Democrats is actually at risk after Trump spent 4 years filling vacancies. They are desperate to create as many vacancies as they can because they know most of what they plan to do is blatantly unconstitutional and they've spent 4 years relying on nationwide injunctions themselves so there is huge risk if some patriots can get a case in front of a non-leftist judge.