Actually, quite often unpaid internships are preventing paid jobs being created - after all, if you can get someone to come and work for some weeks or months for nothing, why pay?
Volunteering can be different, but,,, if volunteers are doing work at community centres, libraries, museums etc. their input can be disguising the fact that there is a shortage of full-time paid staff. The government office reponsible for overseeing these insitutions only sees that work is being done satisfactorily - they don't ask for a breakdown of hours spent on the individual tasks and whether these are being down by paid, qualified staff or by volunteers, some of whom have qualifications, others are just good-hearted, interested people looking for ways of passing the time.
So I would prefer to see volunteering confined entirely to charities and political parties and no volunteers in homework schemes for school-children, or in cultural insititions or the like.