Personally, I am totally baffled by this.
Due in large part to C3's positive influence, Germany is at the forefront of privacy issues and legislation on so many areas, except for this one, which ends up turning into a massive backdoor in the whole edifice. Okay, we can't ask for a copy of your identification card... we'll just use a telephone number or SIM code or something trivially tied back to your IMSI (like an app store account or IMEI) instead. Because of the absurd 2017 law, these are equivalent to your government ID card.
I really don't understand why Germans put up with this while simultaneously pushing so hard for positive changes in every other aspect of online privacy. Especially when so many other developed Western countries do not tie SIM cards to identities: Netherlands, Denmark, Finland, Iceland, Ireland, US, UK, Canada, and many many others.
It's like a giant `sudo gimme-your-identity` backdoor in all the other data collection protections. And nobody seems to care about closing the backdoor.