The interest rates on credit cards are often determined by your risk profile. Your rate will be determined by the credit card company once it evaluates your credit score. You probably have a credit score that is below ideal if you have a high credit card interest rate.
This does not, however, imply that you have a low credit score. Due to the great perks they offer, certain credit cards are made specifically for those with excellent credit.
Therefore, even if you have a really good score, it could not be as high as you would like, and this will show in the rate you receive.
If you violate the card's terms and conditions, your credit card rate may also rise. If you have skipped payments or made late payments on your account, some card issuers charge you an interest rate penalty.