We didn't automate muscles generally, only specifically. The leverage those specific situations have is so high it's worth it. Same with thinking, it's very far from automated generally. Maybe one day we'll have humanoid robots as generally physically capable, and AI as generally mentally capable, but that's a long way off. Until then there's still emmense value for humans in between the high-leverage areas, and even more value in adding some leverage throughout (like the first attempts at exoskeletons, or using Claude to help manage your daily tasks, etc.)