Except you'd probably hire more interns since you don't have to pay them.

Also it's fun to be a king.

Ultimately it comes down to supply and demand.

If there is a sufficiently large pool of potential interns who have the appropriate skills and who are willing to work for nothing then intern pay will be low (or zero).

If, on the other hand, the company looks on interns as part of its graduate recruitment program, wants to hire the very best possible candidates in the US and is in fierce competition with other employers to hire those people then the compensation and benefits offered will be high.

By not paying interns at least a living wage companies are excluding from consideration any candidates who simply can't afford to work for nothing no matter how well qualified they may be.

Just like companies that eliminate employment candidates for any number of frivolous reasons.

And in our area, with the number of decent uni's, there's no shortage of top talent, who can afford it.

So just like anything else, it's all down to location and local market because no company is going to relocate a student for a internship on their own dime, not around here at least.