Reasoning
Warcraft Tavern's Druid guide recommends Leatherworking because it covers gear for every Druid form and Forever adds many new Leatherworking patterns plus a Camp Tent object that grants a Rested XP buff. Herbalism is paired specifically because Forever lets Druids gather herbs while in Travel Form, speeding leveling, and Herbalists get an Incense Candle camp object granting Intellect useful for caster/healer forms. A second, unverified source frames the Druid choice more generally as Skinning + Leatherworking (self-sufficiency) or Herbalism + Alchemy (income), broadly consistent with Herbalism and Leatherworking both being strong picks. Source picks: Warcraft Tavern Druid guide: Leatherworking + Herbalism; Koroboost (unverified): Skinning + Leatherworking OR Herbalism + Alchemy.
Confidence note
Analysis built from sourced profession facts