If they leave the company, their access might be left running for a while in case they're asked to come back on and fix something during that post handover peri

If they leave the company, their access might be left running for a while in case they're asked to come back on and fix something during that post handover period. Or maybe they had backups running under their account and when their account was disabled everything failed so they re-enabled it while they sorted out the mess... Or they had multiple accounts as part of "security" and HR only knows to disable one and didn't find the other one in time. There's a whole bunch of reasons why shit like this goes wrong. Every time. You'd cry.