Not everyone gets time to do voluntary work. Others choose to take on voluntary efforts irrespective of time commitments.
For me, not only is voluntary work a blessing, it is also rewarding and fulfilling. Rewarding because of the skills one acquires, like interpersonal skills, leadership skills, time management, and many other skills. Fulfilling in the sense that you are doing something that makes a positive difference in the lives of others!
There are times when voluntary work gets frustrating, especially when there are inefficiencies or more likely when your ego gets in the way. However, when you treat voluntary work as a blessing and a privilege, nothing frustrates you because you have a goal larger than self!