You think the manager's problems are over if they fire the bad performer? First of all, it's usually pretty difficult and expensive to fire anybody (which also involves onboarding and training a replacement). It reflects very poorly on the manager, so it's not done lightly.

Moreover, after the report has been fired, there's probably still a mess to clean up. Obviously it's not the report who needs to take care of it. It's whoever is responsible for that area, meaning the manager or whoever they can assign to that task.

I'm not saying there are no consequences for an individual contributor who makes a mistake. I'm just pointing out that, at the end of the day, a manager is responsible for the actions of their reports. That's the whole point of their job.