Game Download Sizes Thoughts

With the large game download sizes these days, why don't developers exploit existing DLC/Add-On systems to deliver game assets?

Lets say on Steam, a game currently exists of 150GB. Lets say my PC can only render Medium settings at min 60FPS and I only want Single Player mode.

Then the game should be deliver as:

0) Core Game (runtimes, executables, core logic)

1) Single-player Mode (campaign/story mode, cinematics)

2) Multi-player Mode (Net code, anti cheat)

3) Low Assets Pack (optimized for 1080p, 8GB RAM, 8GB VRAM, Max 15GB Textures/Audio)

4) Medium Assets Pack (Optimized for 1440p, 16GB RAM, 16GB VRAM, Max 30GB Textures/Audio)

5) High Assets Pack (Optimized for 2160p, 32GB RAM, 24GB VRAM, Max 50GB Textures/Audio)

6) Other incremental deliverables or third party packages.

Or a combination of the above. Delivered via Steam DLC system as an example. The developer can choose a basic set or the user selects which packs to install at Install dialog. Then the user don't install 150GB+ worth of assets if the user only needs 15GB.

Any thoughts on this? Why isn't games deployed like this? If not via the DLC system, why not have a similar system right next to it to have it separate?