Congresswoman-elect Alexandria Ocasio-Cortez tweeted recently about chatting with workers at a D.C. restaurant and finding out that many of them were also employed by Congress. They had taken up serving or bartending because the pay from their respective Congressional offices was not enough to support them alone.

This ignited a larger conversation about how much interns in all fields should be paid--which is to say, whether interns should be paid at all.

It's still fairly commonplace for interns to receive no monetary compensation for their work, even if they do receive other perks, like college credit. Some internships offer a travel stipend, or even an overall stipend--amounts that are more than nothing but are nevertheless not equal to what someone could earn making minimum wage for the same number of hours.

This is legal because interns are considered trainees who get as much or more benefit from the arrangement than their employers do. They are getting valuable experience in their industries, practicing how to be an employee in a given field, and gaining work history and references for their resumes and future applications.

Internships are undeniably worthwhile. They are often crucial for getting a foothold in tough industries; job candidates with internship experience have an advantage over those without.

But this should be an argument against unpaid internships, not for them.

Not everyone can afford to work for free. Some college students need a source of revenue to pay for their schooling, so given the choice between an unspecialized paying job (say, in retail or food service) and an amazing but unpaid opportunity in their field, they have to choose the former. And for slightly older adults making a career transition, it's not always feasible to go without a salary or benefits for months at a time while waiting for the resume boost of a successful internship.

Some people can work without pay. So they're the ones who get these unpaid opportunities, which means they're also the ones who get later paying jobs on the basis of their prior experience.

This system discriminates against all but the most privileged. The only people able to move forward unimpeded in many industries are people who are already financially secure.

Companies wonder what they can do to increase diversity among their employees, but this is a key element: low pay or no pay blocks many qualified, talented candidates from applying and, by extension, advancing.

If organizations care about attracting and retaining the best candidates, not just the most economically privileged, they should make an effort to pay their interns.