When considering how financial institutions make money and conduct themselves, there are a number of reasons they may not be perceived as trustworthy stewards of private information.
When making decisions about credit-worthiness, some financial institutions have been rumored to hold impulse purchase decisions against their customers. For example, if you use your credit card to buy gas, snacks at a gas station, or other small miscellaneous purchases, this could be viewed as being stressed financially. Banks could then use this knowledge as reason to not approve an APR on a credit card or an interest rate on a loan that otherwise would be justified. You may be deemed unable to make the qualifying payments.
However, the murkiest factor in determining whether banks and retailers rank less than social networks is how they share information with 3rd parties. Many retailers have rewards programs written in legalese that does not clearly state that information will be shared with 3rd parties. Others may share and not even divulge this information to their customers.
It is important to keep in mind though that this does not mean that your institution is not respecting your privacy or behaving in a manner that is antagonistic to the consumer. Read documents carefully and be vigilant.