When you try to predict what will happen it works pretty well to assume that it's all deterministic and get what results you can. When you want to negotiate with somebody it works best to suppose they have free will and they might do whatever-the-hell they want.

When you can predict what inanimate objects will do with fair precision, that's a sign they don't have free will. And if you don't know how to negotiate with them, you haven't got a lot of incentive to assume they have free will. But particularly when they're actually predictable.

The more predictable people get the less reason there is to suppose they have spirits etc motivating them. Unless it's information about the spirits you manipulate to predict what they'll do.