Many years ago...in happier, pre-Republican times...credit card rates were capped to a max of 21% nationally(?), as I recall. Each state also had its own limits and laws..a very "states rights" sort of thing.

When Reagan and his bloodsucking spawn came into power, states control over credit wasn't profitable enough for the banks and particularly since 2001...the credit card lobby ie banks, pushed for and received ( with the requisite payoffs to (R) campaigns...etc) essentially carte blanche control of interest rates. Its makes them more competitive is the claim. Its funny how states "rights" and local control go out the window when profit is involved.

Interest rates are a function of credit score or a long term record with one provider. Some on this site have suggested that "good" customers receive preferential treatment, ie:

credit card companies are extremely lenient and flexible with:

• those who pay off their balances in full each month.
• those who are not habitually late.
• those who manage their credit well (i.e. not have tens of credit cards, and rotate/transfer balances between them just to avoid or delay full payment). 

if such a person misses out or is late on a payment, all they have to do is call the company and ask for an exception---they get it right away and without hassle.

in our cliamte today, that statement is patently untrue with the exception that if you are continually late then you will certainly pay the higher rate or if you are an exceptional customer, just not "good", you may get a break. The rest of you folks are ,for all practice purposes, screwed. Its like this:

1. Credit card companies want customers who carry and routinely service a balance. If you pay off their balances in full each month they don't want you. They make no money and actually lose money, (hence the annual fee and except AME who charges a higher merchant fee for that reason)
   
2. Fees (and obviously, higher interest charges over the initial agreed rate) are a very, very large revenue stream for banks.
   

That being said it should be no surprise that the ever widening mortgage mess is pressuring bank revenue.  Banks are jacking rates on all customers...as a way to make up for lost income from defaulted mortgages... period.... whenever they can and for whatever reason.

• If you have too many cards...and they determine what that number is...your rate will get raised..
• If you average balance goes above a certain threshold..and they determine what that is...your rate gets raised. 
• You debt is sold to a new credit card company...your rate can get raised.
  
• If you have a change in finances ie; layoff, divorce...your rate can get raised.
• Oddly enough if you don't have a certain number of active cards...you credit score will be lowered and you rate will get raised.
  
• Don't use your card very often? Guess what...

Simply put happy credit card use is a moving target. One exception and suggestion are credit cards issued by professional associations and some credit unions whose membership is based on employment at a specific company or in a specific profession...that sort of thing..USAA is a good example. They really will work with you.

BUT, after all it is their ( the banks) money so the only way to absolutely avoid these issues is to simply not or severely limit the use of credit cards. Be advised, If you do, don't plan on buying a house any time soon unless you have a sizable down payment.