Volunteering is wrong imo. I truly believe that a professional should be paid according to his/her level of expertise and competence. A chemical engineer student who does volunteer work lowers the market value of all engineers in that area. Things have their value and people as well.
I would rather stay home than volunteering. I have no idea who invented the concept and how it became a social value. I asked my history teacher and he said it's something that became popular in the 80s and became even more popular on people's resume in the 90s as a distinctive advantage. A candidate who did volunteering would be regarded with better eyes than someone who went to school or didn't do anything at all. Imho there is nothing more unfair especially for students in debt who have better things to do than waste their time on some payless work.