Supposed you work at a convenience store, and knowing that you got no one covering your next shift, you walk up to your boss and quit. Fine. It happens. Your boss might say something or might not, and some of your co-workers might be as restrained, but probably not. You might have been getting piled on the whole time you were there but seen independently, yours was a dick move too, and some one will remember.
Now, it's a real job, a surgery not selling some ciggies and beer. Surgeries can very dynamically scheduled. A surgery bringing together with surgerns and his PAs, the the anaesthesiologist and his assistant, and other surgical fellows and people who just want to watch. A very complex setup of highly skilled, highly busy people can set up within half an hour. Of all this people, anaesthesiologist is expected to be a more flexible of the rest, even though his his is incredibly important too. A highly skilled surgeon too can be pretty flexible because a lot of the pre-op and post-op duties can fall to other surgeons. But if he says he's got time from 6AM to 2PM tomorrow, that's one thing is not going to move.
An anaesthesiologist coming in here and basically throwing a wrench in the works would be known. It would follow her. No one would really care about the treatment she had before because by doing this, she screwed the patient, not the doctors who's been abusing her. She can shut it down and walk away. No one is going to make her work. But everyone around her will make sure she understands what the consequence of her action is going to be. At the next hospital she interviews, if they hear about this, most likely, it is not going to hire her. Her anaesthesiologist colleagues are going to wonder if she's going to leave them high and dry. The surgeons are going to wonder if this girl is going to check out of the work that she want to do.
Other people have similar responsibilities too. A lawyer can't just decide to drop a client because he doesn't like her. You got entered into a client-lawyer relationship, that's going to remain unless there's some serious issues. Some judges, after a hearing, and deep consideration, might let you off, requiring you to refund all the fees so far. Other judges, especially in a circuit with public defender, knowing that if he releases his lawyer, then he's going to have to appoint someone else for him, and that's going to be a drain in his circuit's budget, will try everything to not let him off. Any business contracts with specific performance that you don't feel like completing? Better take Look at the liquidated damage provision before you repudiate the contract. Jobs where you can't simply walk away aren't common, but they exist and they tend to be very important, significant jobs that most of us hasn't had yet.