That’s entirely reasonable and I totally agree with you, however banks are pretty tightly regulated and can’t give away or sell customer information. Much higher likelihood it’s an app on your phone that’s been harvesting your data to a broker, or your data was aggragated from a breach and sold.
No way will they cancel gmail. Google is using Gmail to train Gemini and power their Ad business. It might be a free email service in terms of not having a monetary cost, but you are paying for it with your data.