Productive work is a major factor in psychological well-being. And a lot of people have spent their career being a highly specialized expert in one thing.
Expecting them to abandon that for a year or more in order to instead contribute "entry-level skills" at something else can be difficult. It's already known how retirement can lead to depression and a painful feeling of emptiness -- imagine how much worse that can be in the prime middle of your career.
It's not about the money or whether GDP measures something or not. It's about the ability to contribute what you're best at, where your excellence lies, or having that ability taken away. For many people, there isn't any kind of easy substitute for their primary area of expertise.