Because of they are ugly in vanilla game.
Vault-Tec Workshop required (obviously)
Also try my Human Vault 88 Overseer mod.
Required mods:

Recommended:
Looks Menu Customization Compendium
Asian Face Enhanced
Extended Facial Sculpting
Real HD Face Textures
FSM Body Textures Redux
THE ENHANCER ENB
(may look wrong without it, may be not)
Made with FO4Edit and Face Ripper.
Now you can keep them in your vault.
FAQ:
Q0: I'm afraid to install the mod because it uses extended facial sculpting.
A0: Extended facial sculpting is installed in my game, but when i creating character i dont use every slider from this. So you can give a try to install my mod without extended facial sculpting. But there is a 1% probability I used 1-2 sliders from this mod and character may look diffrent than on screens.