Robots can’t promise anything, because they have no free will.
Are you sure that free will can't be programmed? How is it that we have free will? If a robot can be programmed with a value system and desires. And if it can choose to modify or adjust those values and desires. If it can think logically through scenarios comparing both method and end to it's values and desires and make choices. Then can it not be said to have free will?
Kinda like a liberal.