Turkey goes further and requires registration of phones, too.
Turkey is not an European country. Having a few percents of the territory in Europe does not move you to Europe.
In Austria and Germany you can't get any SIM without ID as of now.
So if you are a criminal that needs disposable SIM cards you just pay some cash-strapped person to get a bunch of prepaid ones for you.
The point is you have a path to trace if needed. Say some criminal has done that, they've established some kind of contact with the "cash strapped person" to do so - either electronically or in person. Electronic traces are pretty feasible for major nation states to uncover since they're ingesting packet traffic metadata from the whole internet traffic of countries. In-person traces can often be covered by surveillance camera records etc etc. Once there is a point of entry, there is usually a path for entities with governmental powers to investigate.
If you are a criminal, then you can just buy SIM cards from someone or from country that doesn't require indetification.
Do they also make it illegal to sell SIMs between private parties?