Yeah, I know. 6 bucks. Insane savings...
To be honest, no, it's not entirely necessary depending on your setup. If you don't need RAID drivers while setting up Windows XP or so, then you can do without it. It's safer to have a floppy disk around but you can always take it out of an old machine and have it temporarily in whatever setup you need. Alternatively, people have reported successes with external floppy disks. If you have some external HD controllers or the like, it's possible that they need a floppy disk to flash. Your motherboard may require it for flashing as well but these days, they can do it from the USB etc.
I look at it this way - when you suddenly need one, you'll kick yourself for not getting one earlier but most people hardly ever touch their floppy drive during normal usage if ever. I still find it quite useful for some of the recovery programs I have but they (now) come in CD flavours as well.