system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why can massive video games like the witcher or elder scrolls come on a single disc, but most TV shows always come on around 5 discs?
gpt
Because video isn't generally a small thing to carry, whereas 3D data can be. 

Video is just being read and played back, all the data you're seeing has to be there on the disk, otherwise, well, there's nothing to play. 

With something like Elder Scrolls games however what the disk is storing is 3D asset data, which for want of a better word are just instructions on what shapes things are, where certain lights are, what the colour or texture of this particular surface is, and so on. 

The actual 'video' you're seeing is being generated on the fly by your graphic card. It's not like every view you see is being pulled off the disk, it's being generated. 

*edit* To address a criticism of this answer - it's true texture data can be enormous in modern games, but if you scale both sides of the argument, for a modern game compare to a Blu Ray box set, rather than an older game and a DVD box set, the same differences still apply, for the same reasons.