In my point of view, most hiring requires a form of internship. No one drops on to an established team with full knowledge and experience with the internal tools, procedures and products.

And yes, I lament that internships are so maligned. It shouldn't be that interns are poorly paid; we should be able to hire someone with decades of experience in a tangentially-related field at a competitive salary, and consider them to be interning on an unfamiliar field.

Internships are probably the best way to hire, but they only work for people at that specific stage of life.

University students already have a three-month gap in their schedule where they aren't doing anything, so they are willing to take a temporary role to fill that gap.

Experienced people who already have a job aren't going to drop that to take on a temporary role unless they have an unusually high risk-tolerance or unless they are desperate.