I find my bank card handy too, although typically I use it more for cash withdrawals than purchases. I use it for purchases when someplace doesn't take American Express. The latter is my favorite charge card since it requires full payment every month and helps me avoid getting into the Credit Card Interest Pit of Despair.

And, yeah, they can tell where I get cash and what I buy. The grocery store coupon card keeps track of what I eat too, I suppose.

The hard truth is, almost all digital information about us and our spending habits in the U.S. is probably available to anyone willing to dig for it, or with the right warrant. I don't have to like it, but the alternative nowadays is to move into a log hut and just plain don't participate in civilization.