Internships in the Netherlands are akin to modern slavery imo. You work full time and with luck you get a compensation of 500 euros a month,though often no compensation is more likely to be the case. You will get a maximum loan of 1100 euros a month from the government, so a lot of students have to take on a second job if they don't get any compensation at all at their internship.
National institute of neuroscience provides no compensation whatsoever, and for applied mathematics students the average compensation is around 200 euros.
Obviously not wholly related to your comment but the internship situation in the Netherlands really grinds my gears.
Your employer has no obligation to compensate for your internship, but is not prohibited either. There is no minimum or maximum amount set for this compensation.
The focus for internship should be on training, not work. If the Inspectie SZW (employment auditor) finds that the internship consisted of mostly paid work, the employer will be ordered to salary the intern according to normal wages [effectively, minimum wage].
However, there is a practical limit to compensation: students earning more than E20,000 a year are no longer eligible for the student loans you mention.
Student visas?
Hmm...I don't think you are correct, or possibly you are misconstruing a limited, special case to generally apply.
From my own experience I earned more than 600eur as an intern in the NL, and I had classmates who earned full minimum wage as interns too (~1200eur).