Here's why:
* Sharpness: Fully retracting claws would make them less sharp for hunting and climbing.
* Walking: Semi-retraction allows them to walk silently on soft terrain.
* Climbing: Semi-retractable claws provide excellent traction when climbing trees.
So, while their claws aren't as fully retractible as a cat's, they are still very sharp and effective for hunting and navigating their environment.