>>314819971Compare skyrim's DLC to, say, Red Alert 2 Yuri's Revenge Expansion Pack
Skyrim's DLC adds new areas and new missions and some new equipment
Compare that to Yuri's Revenge where it's an entirely different game with new campaign, new faction and an entirely overhauled game balance that makes RA2 multiplayer completely different to YR multiplayer. The base and the expansion were so different that they had to be run differently from different executables. YR could have been a different game but it had to share assets with a base game base game because it's more of an informal sequel that didn't have enough warrant to create a new engine and assets.