I'm not sure it's so much about dealing with hard problems 8h a day, I don't think most people do. But like you say, there's no slack left in the workplace, which makes it ever harder to go into "diffuse" mode thinking. Scrum, standups, email, Slack, open office floor plans and other interruptions of all kind prevents the brain from ever relaxing. Unfortunately, besides just being unhealthy it's also quite unproductive because we need to switch between focused and diffuse modes of thinking many times during a day to effectively solve problems and see the bigger picture.