Internships are a form of on-the-job training. It lets people get some experience on their resume before they leave school, so that they (presumably) have an edge once they are out in the job market. Being able to apply to a position and say that you already know the basics of the role can be the difference between landing the position and having to keep looking.
So my summer time job as a go-fer in the mail room of the print shop of the USDA was really an internship?
All these years I thought it just $2.50 an hour. Maybe I should have gone to Woodstock after all.