NOT PAYING is a reasonable bit of evidence one could use to conclude a theft had been intended.
Try it at WalMart.
The difference is the methods of billing, yes?. No one ever receives a bill for services rendered at the time of an emergency room treatment... If one leaves the hospital pharmacy without paying for a prescription, then yes that’s theft. But I’ve yet to see a cash register at the checkout of a hospital emergency room. If that was the expectation up front then your Walmart analogy would be relevant.
Regards