I had to use a rw cd just the other day, to burn a bootable Ubuntu disk.
Any cd would have done, I suppose.
They are still useful for playing music in cd players, especially in a car on on holiday. There are very few laptops that play music well at volume without using either headphones or external speakers.
Handy too for putting pics on and sending to ancient relatives who don't have a computer but does have a dvd player that will display from a cd.
I don't mind giving cds away, but I'm not so free with memory sticks.