Here's what I don't like about it, as someone who has worked for non-profit organizations that had a lot of students applying to volunteer so they could get their required hours: it can be a huge pain for the organization! Yes, you get some students who are enthusiastic and really contribute. But you also get some who don't really want to do it, who are less than kind and pleasant to the people they are working with, who don't do what they've been assigned to do but instead spend their time talking on the phone to their friends AND then want you to sign off that they completed their hours (well, they were THERE so that should count, in their minds). Meanwhile, you now have to either do the work yourself or find and train another volunteer.
Yes, I think volunteering and community service are valuable. But it is not fair to put already stretched organizations who are trying to help people and animals in the situation of dealing with reluctant students who don't actually want to help but need the hours.
Teresa