It was always just "do your job, don't cause problems".
And for free. Of course. My uni literally bans us from being paid. If we do, they won't acknowledge it as internship.
Could there be any explanation for such a rule, that is not corruption and exploitation? I cannot think of any.
Cynically it feels to me like it's just a nice way for the companies nearby to get free labor.
My assumption for that is just that it's just supposed to be an internship somewhere where our focus would be to study and thus we shouldn't get any benefits from it, but I've never heard of it working that way. It was always in IT here just being an unpaid junior.