It’s actually a myth that carrying a balance does anything to your credit score. Low utilization of your credit limit and long history of the credit line, combined with history of on time payments is what matters.
You get a higher credit limit if they think your income is higher.
Also, parent poster is likely paying interest, which is the worst thing you can do on a credit card.
And yet I regularly have credit karma and others go up-down if I pay off before or after the company reports "average monthly balance". Its usually by a large amount too, 15-30 points.
Utilization has the lowest impact on your score. By your reasoning, homeowners with a mortgage should have a terrible credit score, when in fact it’s usually the opposite.
Utilization is 30% of your credit score making the 2nd largest single factor, behind only payment history (35%). That said utilization only counts revolving credit sources. That means installment loans like home and auto loans are not part of that particular factor.
You get a higher credit limit if they think your income is higher.
Also, parent poster is likely paying interest, which is the worst thing you can do on a credit card.