It's because the Rangery fantasy elements require distinct rules.
Like Ranger Animal companions requires creating Beast Companion stat blocks and the rules to use them.
You can't just Roll Animal Handing and have an Animal Companion
Same with Medicine, Religion, or Nature. You can't roll a skill to heal or find a healing herb.
Copying Wizard and Druid spells is WOTC borrowing spell rules rather than rewriting new rules.
Ideally I think if each Skill was given its own Subsystems, then you could have each Expert class specialize in 2 skills to get access to 2 Subsystems
Skill | Subsystem | Classes |
---|
Athletics | Strength Maneuvers | Rangers, |
Acrobatics | Dexterity Maneuvers | Rogues |
Sleight of Hand | Cunning Strikes | Rogues |
Stealth | Shadowcraft | Rogues |
Arcana | Arcane Magic | Bards, Rangers, Rogues |
Investigation | Intelligence Maneuvers | Bards, Rangers, Rogues |
Medicine | Potioncraft | Bards, Rangers, Rogues |
Nature | Primal Magic | Bards, Rangers |
Religion | Divine Magic | Bards, Rangers, |
Anima Handling | Beast Companion | Rangers |
Insight | Wisdom Maneuvers | Bards, Rangers, |
Perception | ??? | Bards, Rangers, Rogues |
Survival | Ranger Lore | Rangers |
Intimidation | Charisma Maneuvers | Bards, Rogues |
Performance | Bardic Magic | Bards |