Which is still weird.

Alexander Sawchuk, then an assistant professor of electrical engineering at the University of Southern California ... along with a graduate student and the SIPI lab manager, was hurriedly searching the lab for a good image to scan for a colleague's conference paper. ... Just then, somebody happened to walk in with a recent issue of Playboy. The engineers tore away the top third of the centerfold so they could wrap it around the drum of their Muirhead wirephoto scanner...

https://en.wikipedia.org/wiki/Lenna

Everything about the story sounds like it was a rush job, a decision made on a whim, after exhausting their existing catalog of test images. And who bring a Playboy mag to their university's computer lab, and advertises their possession? They don't even say who it was, probably to protect them from any embarrassing professional consequences. To me, that's probably the strongest reason to retire it: it's unprofessional.