Precisely that. If we would learn to value such small things like voluntary work maybe our society wouldn't be so materialistic. I had the chance to work as volunteer twice and the lessons i learned went beyond material value. It taught me to value my work and to take others needs in consideration as well. All companies should have some form of volunteer work program for their employees in my opinion.
Volunteering is a great thing and all. Nonetheless, though, it seems like people aren't really looking at it more closely. Note, a lot of people use volunteer work as something for their resume. In that case, in a sense, it's not really charity. However, these same people might be wanting a pat on the back.
For me, it's experience. It's also nice to help the people in need of course, but mainly I like it for the experience to add to my portfolio. I know a lot of my friends did volunteer work for about a year or two just so they could gain experience and move on to better jobs in the future. I can't say I'm planning to do the same since I'm really aiming for big companies the moment I graduate, but if I ever need to, I wouldn't hesitate doing so.
As I see it, volunteer work has two sides.
The first side is that we, obviously, enjoy giving back to our society just a little bit of what it provided for us. If we're lucky enough to be in the position of doing volunteer work, then we should use that time and energy in providing for individuals, centers or institutions that might need it!
On the other, more materialistic and less altruistic side, it's also a good experience for us to get used to the working field and get a glimpse at certain things and activities that we might enjoy. Who knows, more than one job was born out of volunteer work! If it gives us enjoyment, experience, and we get to help out others while at it... I think that's more than enough to justify its importance!