Because up till now the quaint Bible rule of thou shalt not kill (unless it was in writing that this was you wish or you were as of yet unborn) was the law of the land.
But the right to end your life on your own has been acknowledged, so there should be a regulation for cases when you can´t express your own will. Here, the case would be clear: if the husband and parents don´t state a similar will of the affected person, there is no right to switch off the machines.