SE adds NPC hairstyles as player character options. Players then rage about clipping issues once they're implemented.

Those unique hairstyles are part of the NPC's unique model, which is why they don't clip on the NPC, as opposed to being an interchangeable part like player character hairstyles. Even if SE were to create copies of those hairstyles that could be used on player characters, and add the exact same clothing as glamour options for player characters as well so we could use them as a set, we'd still end up with severe clipping issues that players would be complaining about.

Are you really going to be happy if those hairstyles are always clipping? When they're turned into just a skull cap because you want to display your equipped head item and it's design isn't compatible with the hairstyle?