Yes, I know. But having many IDs means that your information cannot be found by the same ID in all offices and actually many companies, too. That's the way it works in Finland (Sweden, too). While that is a data protection nightmare from a German perspective it should at least allow efficient processes. But as I wrote efficiency is increasingly suffering in Finland, too.

Several of these IDs change when you get a new Personalausweis, Reisepaß, or Health Insurance, respectively. They don't identify you, but the document or contract. Some of the tax identifiers might be specific to you and a tax authority, ie change when you move to a different Land.