The longer a person is kept in the dark about a data breach the more time thieves have to exploit that information. A quick example is if your SSN, DOB, etc. was released multiple credit cards could be opened up in your name and maxed out without your knowledge. This can be averted by freezing your credit report, changing key information on all your major accounts, and generally avert the worst case scenarios, but only if notified in a timely manner. Majority of people only check their credit report once a year and that's plenty of time to ruin someone financially.