Credit utilization is another element though. It's bad if you have too big a line of credit, but good if you have a historically low ratio of (debt/available credit).

In that your credit score has a factor of actual debt to total credit. Someone with $1000 of debt on $100,000 in credit is much better off than someone with $1000 of debt on $5,000 of credit.

So things like car loans and mortgages could be bad, since they start at 100% and go down.

"A credit card would give me the ability to instantaneously take on $10,000 in debt. I don't want this." is a responsible and admirable position for someone to take.