[quote=@Nimda]
<Snipped quote by The World>

Save slots actually have very little space requirements. You just have to store a few variables.
[/quote]

True, but the issue here is that each game instance is entirely randomized. Every single npc will have a look, name, skill set, stat set, item set, level, etc. that's randomized on creation of a new game and dynamic enough to change over time through the game. Even which endings are possible are random because of this.