Unpaid internships, probation etc. historically were created because you'd have completely unskilled labor that wanted a job, and for the company it would take resources to train the person on the job. Which made sense a century ago for the industries of the time.

However, in the modern age, companies require a certain amount of skill for even the most entry level job and the colleges kind of take over some of the responsibilities of training the unskilled labor. At this point, unpaid internships no longer are about companies sinking cost into people without reaping benefits.