That's because we had our own system established in 1984 (ELV, electronic direct debit based on the EC cards mentioned elsewhere). From a German point of view, a credit card is a downgrade.
- The system covered all German banks (private banks, public banks = Sparkassen, credit unions) because they got their act together and set up a single standard.
- It had lower fees than credit card transactions.
- Pretty soon the card was included with bank account fees, while credit cards cost extra.
- It worked with a magnet stripe and automated electronic clearing in a time when credit cards were merely a slight convenience over manually writing a check which needed to be mailed around the country (you do know why credit cards have name + card number embossed to this day, right? Check out credit part imprinters).
All that made it more attractive to merchants, and credit card companies weren't used to competing in a market that already had a big incumbent.