Last I remember, even though the four main races had hair tissues, only Dwarves and Humans had the right creature tags to have styled hair. But the Human entity lacked the tags to allow them to actually use these stylings, last I checked. Add these somewhere in ENTITY:PLAINS for Humans, ENTITY:FOREST for Elves, and ENTITY:EVIL for Goblins in the entity_default file.
[TISSUE_STYLE:HAIR]
[TS_PREFERRED_SHAPING:STANDARD_HAIR_SHAPINGS]
[TISSUE_STYLE:SIDEBURNS]
[TS_PREFERRED_SHAPING:STANDARD_SIDEBURNS_SHAPINGS]
[TISSUE_STYLE:MOUSTACHE]
[TS_MAINTAIN_LENGTH:100:NONE]
[TS_PREFERRED_SHAPING:STANDARD_MOUSTACHE_SHAPINGS]
[TISSUE_STYLE:BEARD]
[TS_MAINTAIN_LENGTH:100:NONE]
[TS_PREFERRED_SHAPING:STANDARD_BEARD_SHAPINGS]
Elves and Goblins do not have the tissue tags to style their hair in neither their creature definitions nor their entity definitions. These are the creature tags, I believe.
[SET_TL_GROUP:BY_CATEGORY:HEAD:HAIR]
[TISSUE_STYLE_UNIT:HAIR:STANDARD_HAIR_SHAPINGS]
[TSU_NOUN:hair:SINGULAR]
[SET_TL_GROUP:BY_CATEGORY:HEAD:CHEEK_WHISKERS]
[PLUS_TL_GROUP:BY_CATEGORY:HEAD:CHIN_WHISKERS]
[TISSUE_STYLE_UNIT:BEARD:STANDARD_BEARD_SHAPINGS]
[TSU_NOUN:beard:SINGULAR]
[SET_TL_GROUP:BY_CATEGORY:HEAD:MOUSTACHE]
[TISSUE_STYLE_UNIT:MOUSTACHE:STANDARD_MOUSTACHE_SHAPINGS]
[TSU_NOUN:moustache:SINGULAR]
[SET_TL_GROUP:BY_CATEGORY:HEAD:SIDEBURNS]
[TISSUE_STYLE_UNIT:SIDEBURNS:STANDARD_SIDEBURNS_SHAPINGS]
[TSU_NOUN:sideburns:PLURAL]
Add these somewhere under SELECT_CASTE:ALL. Preferably right before the line that defines skin colours, as that is where they are entered for Dwarves and Humans.