I worked with a lot of interns, and in my experience the ONLY value was finding folks randomly who were good enough to hire. The actual productivity / work for the interns on average was very low.
The rate was so low though that I'm not sure if it really was a net positive, but I think the company liked the PR and such too.
I mean yeah, that's not really a secret. The head of the intern program that I was at straight up told all the interns that it was worth it to the company if even 20% of the interns who were hired returned as full time employees.
We sometimes get completed usable work out of interns, but it’s much more a recruiting vehicle (for us) and a training/pay it back for the candidates. The recruiting can pay off for a decade when you land a star out of college and retain them.
The rate was so low though that I'm not sure if it really was a net positive, but I think the company liked the PR and such too.