IMHO obvious why
The factual robot is passive and task-oriented, so one assumes that, having no further orders, it will simply remain on standby like a computer.
The chatty robot on the other hand is active, and thus has to be actively constrained.
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One is an appliance, the other a pet. Appliances don't need to be constrained, and their inner workings are often non-obvious (remember subjects telling they were worried switching it off would compromise the test). The pet on the other hand is an independent organism we are used to dominate and control, no matter their begging. Switching the chatty robot off is in the line of putting the cat/dog outside for the night, for instance. Begging is expected, and thus inefficient.
Biting the hand that feeds IT
