I was sitting at a desk last week and overheard a man yelling down a phone to someone else that "People aren't an asset. They don't appear on a balance sheet". I agree with that view - not because of the strict accounting definition of an asset, but because of what I believe people in companies should mean (either consciously or subconsciously) when humans are called assets.
Companies refer to humans as assets for 2 reasons. (1) To make employees feel good and (2) because of the value they create for and contribute to the business.
I believe humans are assets to companies, but they are not assets of the companies. The actual asset belongs to the individual - their time - and they trade it for money. The company gets the output of that trade, but the value of the asset remains in the power of the individual.
They won't appear on a balance sheet, but the work they do with their time that they have swapped for money is the "asset" in the eyes of the business. That appears on the books in the form of IP, physical goods, inventions, patents, or money received for the company on-selling that time (like the work I do).