Real people have real families. Kids grow. Parents age. Sisters have car accidents. Dogs rip their ACLs. At any moment any realworld person may have to walk away from the job they love to accommodate the needs of a family member. Maybe they need to go to a higher-paying job (if they are lucky) but more realistically they need a job at a different location or time so they can spend more time dealing with things totally outside the job.
Real people have real bodies. They get sick. They have heart attacks. They get devastating news from doctors. They need to spend less time at the keyboard and more time at the gym. The job you love, that you are willing to spend 24/7 working to improve, is often the job that is killing you.
Want to keep employees onboard? They want two things more than anything else: Either more money, fewer hours for the same money, or some balance between the two. That's what keeps people from leaving. It allows flexibility when that day comes that they would otherwise have to walk. Everything else is just icing on the cake.