It depends on their sleep habit, work-life requirements and compensation when they need to be on-call.

When you get a fatter check because your code break, the incentives are not in favor of good code.

That depends on how quick the feedback loop is for your decisions. If it takes weeks or months to find the impact of your changes, or worse, if you're insulated somehow from those changes, you may not be pushed toward improving the quality of your code.