Many times people quote such dignitaries or such luminaries as Swami Vivekananda while teaching people to do work for social good. Though it is very inspiring to know the work of Swamiji and such other luminaries, one must never forget that most such highly venerable persons first complete their sadhana (spiritual practice) and achieve the final goal of such a practice. Later, they come into society and serve the society. Such persons have different inside and outside. They are not attached to people and their happiness does not depend on what people do. They are really doing a Nishkama Karma. Nishkama Karma (the one which has no expectation from others) depends on the fact that one has no desires from outside for oneself. But, this is possible only if one has satisfied all the desires one has and one has no more desires left. The ultimate desire is the Spiritual Realization. Such luminaries have satisfied such a desire and therefore they do not have any desires.
For other people, it is not possible to work that way. Therefore, the only way the other people can work is to do the work as a Karma Yogi. Karma Yogi has not yet become Nishkama Karmayogi. Karma Yogi only does work as a duty without getting attached to the fruit of action. That means, Karma Yogi accepts whatever the outcome with happy face and goes on doing the intended duty. Thus, the Karma Yogi is not serving the society fully in its real sense. He is only doing a spiritual practice of Karma Yoga. Later, he/she is likely get realization, after which Nishkama Karma Yoga is possible.