Why does/would a "Bodhisattva" burdens himself and instigate others as well?

Why does/would a "Bodhisattva" burdens himself with the choice of becoming a Buddha (avoiding extinguishing dukkha) and instigate others as well to do so? Given that this world is full of "Bodhisattvas", there is not one being who is not just here to help others out, why does a Bodhisattva instigate others to stay on this normal course of birth and death? Does he need food to nourish his undertaking and fearing to find nobody and nothing as reason for further becoming? Or what is the reason to instigate others to do such a work? Just to become one day wise and listen to what the Buddha say and trap others who have the same blindness for it? (Given that the Teachings of the Buddha of our time is still available) Or do they assume that there are no teachings which lead them out for now?