Not at all. Charity/public good doesn't imply free work. And it's still up to the company to provide work that generates value for themselves. It's not free on either part of the company or the intern.
I don't know what the case is in the US, but in Canada, the government does provide some taxable benefits to the company for hiring interns or people between 18-24. I don't know the specifics, but they do exist.