Precisely - they view security as just one part of many of their business, instead of viewing it as one of the most important parts. They've insured themselves against a breach, so it's not a big deal for them. But it should be.
The more casualties, the more media attention -> the more likely they, and others in their field, will take security more seriously in the future.
If we let them do nothing for a month, they'll eventually fix it, but in the mean time malicious hackers may gain access to the PII. They might not make it public, but sell that PII via black markets. The company may not get the negative publicity it deserves and likely won't learn to fix their systems in time and to adopt adequate security measures. The sale of the PII and the breach itself might become public knowledge months after the fact, while the company has had a chance to grow in the meantime, and make more security mistakes that may be exploited later on.
And yes, I know it may be a crime - that's why I said I'd report it anonymously from now on. But if the company sits on their asses for a month, shouldn't that count as a crime, as well? The current definition of responsible disclosure gives companies too much leeway, in my opinion.
If I knew I operated a service that was trivial to exploit and was hosting people's PII, I'd shut it down until I fixed it. People won't die if I make everything in my power to provide the test results (in my example of medical labs) to doctors and patients via other means, such as via paper or phone. And if people do die, it would be devastating, of course, but it would mean society has put too much trust into a single system without making sure it's not vulnerable to the most basic of attacks. So it would happen sooner or later, anyway. Although I can't imagine someone dying because their doctor had to make a phone call to the lab instead of typing in a URL.
The same argument about people dying due to the disruption of the medical communications system could be made about too-big-to-fail companies that are entrenched into society because a lot of pension funds have invested in them. If the company goes under, the innocent people dependent on the pension fund's finances would suffer. While they would suffer, which would be awful, of course, would the alternative be to not let such companies go bankrupt? Or would it be better for such funds to not rely so much on one specific company in the first place? That is to say, in both cases (security or stocks in general) the reality is that currently people are too dependent on a few singular entities, while they shouldn't be. That has to change, and the change has to begin somewhere.