Certain course are required for academic development, and yet there is no course required for emotional and social development. We go to school as a whole human being, and not just as brains needing nourishment. We get so wrapped up in ourselves, in getting good grades or scoring with the "hottie of the moment," that we forget there is a real world outside that needs fixing somehow, and that we can do our part.
If service learning is done properly (beyond mere volunteerism/helping) it can reinforce lessons that are being taught in classrooms. It allows students to see, outside the classroom setting, the depth and scope of what they are learning. For example, when being taught about issues related to race, class, and gender, service learning in locations where students see and experience, first hand, the experiences of people who are of different races, classes and gender can reinforce the classroom experience. In addition to lecture, our bodies have a different way of knowing. Sometimes you have to be in the environment to be able to "see" what you've learned. Additionally, service learning should require some self-reflexivity, in order to tie it back to what is being taught and to think through the process of engaging in service learning.
Service learning teaches kids volunteerism and societal values in school. Perhaps one semester of volunteering for a certain organization in high school is one way to teach teenagers the value of such groups and why volunteering is an important part of society in general. Without services and non-profit groups, contemporary society comes to a screeching halt.
I don't like service learning, its pointless, go figure it out yourself. People shouldn't depend on students to do things for them. That is a child labor and is very illegal. I do not like it because it is not fun. What college is going to look at that? Its not important
Community service is something that should be done under your own free will. By forcing students to participate in community service, it takes the point out of community service and students will consider it to be a hassle rather than something that they are doing in order to better themselves and the community.