It's interesting because when dealing with inanimate objects, the term manipulation is pretty neutral. It's only when we refer to people that the term manipulation takes on a negative implication.

I think it's the lack of reciprocity that's the difference. If someone manipulates me to be more productive at work, but I don't see any benefit in return, it's different than if I get a raise or a bonus as a result.

Even if I do get a raise or bonus, the manipulation can violate a personal boundary, and as a result, have mixed positive and negative consequences.