> your employer pays for it

Well, in the end the employer has reduced your salary by that amount, employers are not known for welfare. Every employee is already entitled for full public health care. Something must be wrong with it if 90% of the employers offer double insurance in away. It's a public secret or gentlemen's agreement that employed people are not supposed to use the public health sector they are entitled to before they need specialist or hospital treatment. The gentlemen's agreement would stop working if basic public healthcare were reasonably good.