The power clean teaches explosion. It cannot be done slowly. And since it involves a longer pull than the squat clean, it emphasizes the finish, where the maximum hip, knee, and ankle extension occurs, without the added complication of the front squat part of the movement.
There will be a weight, however light or heavy, that the athlete can handle correctly. That weight can be gradually increased, enabling athletes of any level of advancement to increase power production. Since athletics depends so heavily on the ability to exert force rapidly, the clean is a very useful tool for all athletes