Volunteering - Self interest or self sacrifice?

This questions has been posed quite a few times.
A person may volunteer for many different reasons; for example some might have a moral obligation to volunteer but on the other hand some may volunteer because they may receive a direct or indirect benefit from it therefore a more self centered approach. I believe, regardless of the reasoning as to why people decide to volunteer, the only thing that should matter is that individuals are willing to help and give up their time for a good cause; lending their hand to lead the way for societal change.