- If you want to pay bills you just do a bank transfer (they are free and fast within the EU), transferring the money to a published bank account with my invoice id or similar in the subject. If somebody else wants to pay my invoice neither I nor the company will have any objections, so no need for authentication.
- If I want to check a bank account or a credit account or something similar I have a password that was set up when the account was created
- If I want to set up an account I can authenticate either via webcam (showing off the security features of my ID card) or via PostIdent (where I have to go to a post office)
- When talking on the phone you have an authentication problem (unless a "phone passphrase" is prearranged, but for anything with lasting consequences you usually have to send them a written version per email or snail mail for papertrail reasons anyways, or alternatively they send you a confirmation per snail mail that you can object to in a reasonable time frame.
The new ID card has online features that in theory solve the problem completely for online systems, but few places implement that so far.