Because they don't want companies using it as a way to avoid the responsibilities that comes with real employment. The rule is to my knowledge however intended

Because they don't want companies using it as a way to avoid the responsibilities that comes with real employment. The rule is to my knowledge however intended to keep companies in the same country from using it. In Denmark(same rule) I contracted for a single foreign company for years and just got lump sum into my personal account every month, after which I paid the corresponding taxes. I specifically called the tax authorities to ask and that's how they said to do it.