You're not punished at all. Your credit score represents a mathematical risk assessment of your history, your behaviors, your standing. Lenders choose to pay the risk experts for their opinion on how much risk it is to extend credit to you. If you're higher risk, the credit costs more.
If you take the return required on money to be profitable, let's just say, as a hypothetical example, that they have to make 100,000 on 1000000 dollars loaned. One group of borrowers have an average score of 750 and another group of borrowers have an average score of 650. Considering that, hypothetically, 10 per cent of the 750 borrowers will default, they have to pay an average interest rate of 6%. If 40% of the 650 borrowers will default (that's probably a low estimate of defaulters; you have to be pretty much a deadbeat to have a 650 credit score) then they might have a 24% interest rate.
Using your credit definitely increases risk. The more you use your credit, your debt load goes up exponentially since you have to pay more interest. High debt load has been a proven factor in spiraling out of control and leading to default or bankruptcy.