I think most of the size of games is just graphics and audio. I think the code for most games is pretty small, but for some godforsaken reason it’s really important that they include incredibly detailed doorknobs and 50 hours of high quality speech for a dozen languages in raw format.

True. Even Xonotic - opensource game - has very small game engine, but game logic and assets(maps, textures, lightmaps) are 1 gig. And same with AltCraft - small engine, but minecraft assets are huge.