I agree with madworm, also:-
Companies actually incur a real cost overhead by having interns who are paid only their travelling expenses.
We are not saying they don't but what do they actually gain? If it is less than the overheads plus a minimum wage then they should not be doing such activity. That is simple economics.
They are only sponging of everybody else for their own gain. So I assume you are against level playing fields and approve of the dog eats dog and the devil takes the hindmost attitude of capitalism that seems to have got the world into the mess it finds itself in at the moment.