People volunteer for an array of reasons. You will find young people volunteering mostly for one or the other reason. Some of them volunteer to get a firsthand experience of things and then establish something of their own. For example, many young people volunteer in NGOs to understand the dynamics of community service and then graduate on to establish their own community service organizations.
Some people are simply passionate about a cause and want to do something about it as and when they can contribute. Volunteering gives them this flexibility. They volunteer during their leisure and get back to their respective original jobs after a while.
Some other people who are fuelled with a passion to do something for the community and hence they take initiatives in the society and volunteer for a number of things. There are abundant examples of people who have volunteered for cleaning public toilets, parks, roads and other properties, other people who have volunteered to donate their blood or who have volunteered to adopt children for their education.
Some other people volunteer because they want to add some skills in their resume for better careers while other volunteer because their education requires them to volunteer before applying for higher studies.
Volunteering is also a great way to learn about new countries, new cultures and new people. Many people volunteer in foreign countries in order to travel and learn new things in life. Volunteering also helps them pick a new language which is a great asset for any career. Some people also volunteer to get a decent job later in the life on the basis of volunteer work done in past.