When someone as rich and notable as Bill Gates makes a suggestion you assume that it has been well thought through and holds water. He’s made a suggestion on the robotics problem. If automation continues to displace normal human jobs, why not tax the robots — just like normal employees?
If, however, you propose taxing the robots sufficiently to cause the human jobs to be retained then your tax becomes a subsidy and a small number of workers benefit from higher wages. But the price of the product necessarily goes up.
When the price-hike subsequently cycles into the general economy it means that all customers are paying a little bit more for everything than they otherwise would have done. It’s so little that government politicians affect not to notice it. Nevertheless it means that the general standard of living of the population is diminished by a little bit.