It depends. Historically speaking it was manual laborers. In the modern age you could probably include low level white collar jobs. It’s a factor of how much of a physical/mental toll their body takes in proportion to their compensation. For example: CEOs generally make 200-400x their workers pay. If you have a ceo of a mining company making $30,000,000 a year, but you have operators working underground 12 hour shifts for 6 days a week 100s of miles from civilization making only $100,000/yr
I’m not saying the ceo doesn’t do any work, I’m saying the work they do is far less taxing on the body and mind than the average worker, but they’re still compensated. The CEO will have the power to drive company direction to an extent. Meaning - they’ll want to pay them as much as they can to make sure they stay aligned with the boards vision