Plus, once a reference is established (like the floppy disk) it's idiotic to always replace it with the latest tech (we'd have zip drives in the nineties, usb drives in the '00s, the cloud today, etc etc..)
What's the alternative, pick something abstract that confuses people. That didn't work out so well for the recent GMail redesign.
It's thousands of years old, thus despite our ability to record and learn from history, we should replace it with something more modern.
And crashed beige boxes for Windows machines mounted on Macs: http://www.blogcdn.com/www.engadget.com/media/2007/10/generi.... :-)
It doesn't really matter as long as it's roughly ubiquitous, which the floppy drive is. It doesn't even matter if no one's seen a floppy drive; if someone doesn't recognize what the floppy icon does, then the rest of their computer is new to them and they're learning. Once learned, forget about it.
Etc.