Given that they cost next to nothing, do not use up an IDE connection, and can come in real handy in a lot of situations, I don't understand why anyone would not install one in their machine. I mean really, other than "I'm just too cool to have that old stuff in my rig" to me there's just no good reason not to include one.
I got a nice deal on some of the "7-in-1" floppy drives that handle floppies but also every kind of flash memory. Very nice, it just sits in there like a normal floppy (it's the same size too), but you can put in a floppy or any kind of memory......