Just because there's no pay doesn't mean there's no reward.
Volunteers get loads back for the work they do. They get the chance to do something about issues that matter to them and also learn important skills.
They meet people who share the same interests, and get experience for the future. Voluntary work allows young people to show that they have the power and the energy to make a difference.
Most of all they get to be independent and choose what to do, and where and when to do it.