Because they're the ones actually doing it? Because they're run by adults who are fully capable of taking responsibility for their actions?
Worse, it's frequently the same people who argue that corporations are "people" arguing that corporations as a whole shouldn't be held responsible for their actions.
But to use people's lives as leverage to extract absurd amounts of money goes well beyond being immoral, it's just downright evil.
Of course they deserve to be paid. And paid quite nicely, too, considering the education levels needed to work such jobs (Lifeguards, obviously requiring significantly less than doctors)!
But they can be paid nicely while charging reasonable prices. The $164k the hospital charged that man for his heart attack is beyond unreasonable.
FTFY.
But seriously, how can it possibly be the hospital's fault for doing exactly what the law and market incentives give them every reason to do? There's almost no downward pressure on prices: little competition, no transparent pricing, huge barriers to market entry, and third party payers.