Pretty sure I have read somewhere that it is now also an official necessity in Germany

Exactly, sure disconnect customers from the Internet if they use it for entertainment... but once they use it to earn the income that pays their bills, it becomes questionable... and once it is in practice required to be a citizen, at the local, national or supra national level then it becomes a totally different question, to which the answer is basically no, you can't disconnect someone otherwise you remove their citizenship.