Hmm, I guess it depends on the place you buy your computer from.

I've only ever bought computers from stores that assembled them for you on request, and floppy disk drives have always been and still are an option.
Amy, there are different types of CDs: recordable and rewritable. The recordables you can use only once. You put data on it, and you can't change anything afterwards. The rewritables are more expensive than the recordables, but they're more like your floppy disks. You can overwrite files, add files, and use them multiple times.