system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do consoles still need discs even after installing in order to play a game?
gpt
For the newest consoles where the data is installed to the hard disk, it's just to make sure you own the game. The disc is essentially a licence key.

They could have gone with a system like Steam where even if you buy something on a disc, you get a license key that links the game to your account. But that would make second hand sales impossible and console gamers aren't keen on that.