Answer:
- You are not paid for it
- It does not always provide you experience
- The time can be used to work a job where you can make money as well as earn experience about your future career field.
- Having worked a job previously assures the person reading the resume rather than seeing on the resume that the person has only volunteered
Note: Volunteering is better than doing nothing at all, I think volunteering is helpful in many ways as well
