The wise will insist that ex-employers do this, if not immediately, then over a very small number of hours. If I'm to be let go, I want all of my access to go away ASAP. That means they can't blame me for things that go missing afterward (minus logic bombs and other kinds of criminality that we do not do, ever, ok?). The last thing I want is for, say, a computer to go missing a week after I left but when I still have an office key, or data to be deleted while I still have AWS access. Take my keys, OK?