By means of collecting purchasing information, the credit card industry is doing the same thing that just about every retailer is doing by using loyalty cards. They're looking for trends and doing analysis of bulk data, and in the banking industry, at least some of that is legitimately done for fraud prevention.
It's hard to imagine any individual's purchasing power being great enough to warrant the cost of a ongoing detailed examination of their individual data, unless of course you are a man of such YUGELY MASSIVE WEALTH that the system isn't equipped to handle your data anyway (and you want us all to know who you are!).
Even if individual data were personally examined, I'd be hard pressed to think of how or why it would matter. Generally speaking, the card industry isn't going to alienate customers, and neither are retailers. As with loyalty cards, you give up some data to get discounts or cash back in return, but the data that most people surrender in those situations generally doesn't expose much, if any, risk. Go ahead and pay with cash, but by that time I've already collected far more personal data on your purchases and behavior--thanks to the CCTV recording--than I'll get from your use of a loyalty or credit card.
Yes, the credit card industry preys on people who can't pay their bills or responsibly manage their money, but the same is true of state-run lotteries and most of the gaming industry. No matter how much you try to spin it, those industry behaviors aren't a cause, they're an effect. Credit cards can be a useful tool of convenience which also work to protect the financial well-being of the responsible consumer. And no, I don't work in nor am I affiliated with (and neither do I completely trust) the banking industry.
Regarding privacy, I'm far more concerned about the government snooping in my bank transactions for "suspicious" activity, where they get to be the arbitrary judge, jury, and executioner. Home Depot or Chase bank can't seize my assets without a legitimate claim and court order, but the government can if they think that my multiple deposits or withdrawals are "suspicious." And yes, it happens to completely innocent people, and more often than you may realize.
JKG