"Your Email was found in the data dump from the FooBarBaz.NET hack!"
Okay, which site was this? Is there a password I'm supposed to change? Was it actually a password I stopped using 5 years ago, but is still floating out there somewhere?
None of these questions are ever answered in a way that's actionable, so these notices get effectively ignored.
(FWIW, back when I worked at a certain big company and they provided this service to employees, the data dumps actually did contain enough useful info to answer the questions some of the time. But the services available to the general public, even if you pay for them, are damn near useless.)