Engineering internships/co-ops are great, that they are paid is the result of supply and demand. Hard sciences/engineering demand is much higher, compared to the supply, than history/political science/journalism.... I also had a paid engineering summer job after switching majors (and while I went to work in the Congressman’s office expecting not to be paid, they actually had a paid slot available they gave to me), in the right circumstances the opportunity to work for free can provide a tremendous learning opportunity. The problem is the abuse of the “apprentice” situation by those who give meaningless tasks instead of a good mix of more interesting work (committee hearings/research/writing and review of your work with very professional and constructive “criticism”). Fortunately I had very good internships (both paid and unpaid), but I have heard horror stories.
I was at an ‘all hands meeting’ for interns of a major corporation. It was half way though the summer. Part way though the meeting the guy talking mentioned paychecks or some such and let slip a representative number. Half the people in the room suddenly had very shocked looks on their face. A moment later the speaker apologized and said that was an engineering intern salary number... not one for all the HR and business office types. I tried not to laugh at all the shell shocked looks from half the interns in the room.