I think the idea is that it would be nice to allow people to volunteer/intern when you have no other way to give them that introductory experience. If your options are "give people a chance to get some experience without paying them" and "let them figure out how to get that experience in a down economy on their own because you can't afford to pay anyone", I think trying to find "a way around paying them to do work" is actually good for them.

> a simplification might be that volunteers can work free for a charity but not for a for-profit business.

So, what you're saying appears to be that for-profit businesses can't directly do anything charitable without paying enormous out-of-pocket costs, since they can't use volunteers. I think your plan sucks.