Question

Why is Service to humanity our duty​

Answer 1

Society is a tool for humanity. Think of society as being a bunch of humans who realized that they would do better together than alone.

At birth, I think it's fair to say that you don't owe anything to anybody. Since nothing about your birth was truly your decision, the responsibility for the debts thereafter fall on those people who caused your birth: your parents and whoever else might have had a say in that process. That means that your debts are acquired after birth, typically from benefits received, or damages caused, by you.

Because society has such an impact on our lives, I don't think that someone can trivially say that they do or do not owe anything to society; the calculations to determine this would be abundantly difficult. My solution to this problem is think of it in a different way altogether. If the next person to be born would get at least as many benefits from society as you were provided, then your existence does not change society for the worst and you have done well by your debtors, so to speak. So the idea is to simply leave the world as it was or better if possible.

I think that is the extent of one's obligation to society. Taking it from there to the point of dedicating one's whole life to service is a large step, and one that I would consider to be unfair to one's own self. More than anything/anyone else, you owe it to yourself to have the best life that you can.

credits to david gesua