Figure the man (or woman) is really only there to meet legal requirements around having a human somewhere in the loop. The human is a liability, thus the dog. From the interpretation where dog is guarding the equipment, the dog may as well be robotic, sure. But some live animal also provides distraction from the equipment, as well as the ongoing companionship needed to keep the human psychologically stable, which is also crucial for long term liability. Spare human workers are hard to come by, most of them having died of starvation due to lack of employment.

Nor the dog to distract the man! Perpetual motion discovered; nothing shall ever break or change in this factory

Strikes me as odd. Why have either? We're clearly in a fairytale - I just lack context. Probably a complaint with some creative color