Health insurance is mandatory for long-term stays in Netherlands, i.e. if you pay tax you will have to choose an insurer.
It is not mandatory for tourist visits, but you might consider looking at the issue more closely. It's also not clear from your question "who" has "requested" the cover. Can you give more detail?
Not sure where you're from, but even if you're European your European Health Insurance Card will only go so far, most European nations advise their citizens to take out their own medical insurance in addition, to cover things such as medical repatriation to your home country (which the Dutch system will not pay for).
My own government says "if you can't afford travel insurance, you can't afford to travel". about 6 years ago