Holding multiple CC actually can at times increase one's credit score in the US. In US, a major component is the debt-to-credit ratio. Say, one credit card is $1000 credit line with current debt on it of $200. Then say that person applies to another credit card with $10,000 credit line, with same debt of $200. Then the total credit of that person is $11,000 with just total debt of $400. So in the eyes of the credit score companies, the person has more credit, so will be rewarded a higher credit score. Now with that same total $11,000 credit line, if the debt held increases closer to the 100% mark, then the credit score will be a bit lower.

So perhaps in Germany it is done differently, because in the US, the higher the credit limit is on each credit card with lower debt ratio, means the score goes up. Crazy logic right?