Some may accuse the Bhikkhus and Bhikkhunis to be selfish because it could be seen that they are seeking enlightenment for themselves while doing it at the expense of others and that in reality they do not contribute to their communities,however seeing the Bhikkhus and Bhikkhunis in this way would be wrong for a number of reasons. While it is true that some monks may be corrupt and their intention impure, when someone joins the monastic sangha and becomes a stream enterer he is seeking religious truth for the sake ending Dukkha(suffering) in the world as a whole. This is especially true in the Mahayana tradition where the Bodhisattvas(Highest Mahayana Ideal) take a series a vows the most important being that they will reject enlightenment to return to samsara in order to help the rest of the world in achieving Buddhahood and only then will they enter enlightenment. The same can be said about the Arhat in the Theravadin tradition is that upon achieving Nibbana they themselves will be able to spread the Dhamma throughout the world much like the Buddha Siddhartha Gautama did. Another point would be that it would be impossible for a Bhikkhu or a Bhikkhuni seeking enlightenment to be selfish as that would imply the presence of Greed, which is one the three fires which keeps one in samsara.