[cortesoft]

Depends on what you mean by 'should be'. Are you talking about what it morally should be, or what it should be based on historical patterns?

I am guessing that data has shown people who utilize less of their available credit are more likely to not default. Whether that is morally better or not is up to you.

As for the reason this is the case, I am guessing it has to do with resisting temptation and not living right at the edge of your means. Having credit but not using it shows that you have a buffer between where you are and destitution.