They're not necessary, just terribly handy. Want to make a bootable CD-R or USB flash drive? Guess what the boot image is based on? Yup, floppy.
So instead of pirating WinImage or some other program that can read/write ISO files, downloading a floppy image from somewhere, removing the stuff you don't need/want, inserting the stuff you do need/want, creating a CD-R or USB flash drive from the floppy boot image.....why not save seven steps and just use the freaking floppy that all of these other technologies are emulating, anyway?
Bootable USB flash drives are a royal PITA and are not universally compatible with all BIOS. There are at least three different methods to create a bootable USB flash drive, depending on how many of the other methods you've already tried without success.
Alternatives may exist with faster transfer rates and storage capacity, but nothing approaches the ease and guaranteed universality of the floppy.