Early stages of outreach are typically handled by Direct Sales Agents, who reach out to prospective customers on behalf of a credit card company. This is when you receive tons of emails and / or telephone calls for this or that credit card. At this stage, the credit card company is not directly involved. In all likelihood, it does not even know of your existence.
Now these DSAs are independent companies and each DSA runs outreach campaigns for multiple credit card companies. So DSA employees and management have access to contact info of potential customers of multiple credit card brands. While contractual clauses likely forbid sharing of this info inside the DSA company, in actual practice, information tends to leak from one part of the DSA company to another.
Of course, it’s also possible that customer info leaks from one DSA company to another or even from one credit card company to another but those incidents are relatively rare.
Next time when you get emails and calls from multiple credit card companies after showing interest in only one credit card brand, know that all those comms are most probably coming from the same DSA company that handles the outreach campaigns on behalf of all those credit card companies.
Now, this can be irritating to a potential customer but there’s one advantage with this approach.
Suppose you’ve shown interest in Credit Card Brand A. You don’t know it but the DSA running the outreach campaign for CC-A knows that, with your current credit score, you won’t qualify for CC-A. One way of moving forward is to simply tell you that your application for CC-A is rejected. End of story.
Another way would be for the DSA to use its knowledge of other credit card brands and find out another Credit Card Brand B that you would qualify for. Then proactively offer it to you instead of just telling you that you were rejected for CC-A and leaving it to you to start from scratch and do all the work to find another credit card to apply for.
The second approach does involve leakage of personal info but many people, including me, might be willing to accept the tradeoff between loss of privacy on the one side and greater convenience and speed on the other.