CD or DVD media are not expensive where I am (even dvd-9 disks are now a fraction of what they cost a year ago. $5 each or about $1 for dvd-5 disks.) eg: I temporarily copy & burn borrowed videos onto dvd-rw disks so we can watch them when we like if we're pushed for time. Keeping everything on your computer takes up space & adds to wear on your HDD. Burnt as disks they will most likely last longer than the majority of HDD's.
And having a dvd data disk of video music clips (or just music) for example keeps it organised & indexed for easy playback.