Hospitals are a pretty stupid target in comparison to banks, physical retail environments, and online stores. A hospital DB might contain a social security number, addresses, illnesses, and birthdate. So what?
If you can get into a bank, you get money account info, credit scores, security tips, former trades, credit cards, all sorts of good stuff. If you get into a retail environment or online store, it's almost as good. Basically, you get money to spend. In a hospital though, the only unique thing you find out is if someone is sick and with what. That's a pain in the ass to work with. You can try to get more info from all that PII, but again, it's a pain in the ass and available elsewhere. Other stuff is more lucrative for the investment of time, criminal risk, and energy.
If you were a terrorist, a hospital might be a bit more interesting, but the various hospital disasters I have read about demonstrate that there isn't much a hacker can really do to hurt people. Nurses at the end of the day don't do stupid things and doctors aren't much worse.
No, hospitals are a stupid place to expend effort.