> other people are proud of their parenting, their hobbies, their friendships, etc. People can choose to work more or less. But if someone chooses to work less

> other people are proud of their parenting, their hobbies, their friendships, etc. People can choose to work more or less. But if someone chooses to work less, he forfeits the right to complain about being paid less and being promoted slower compared to people who work more. The proposed four day work week would increase this disparity between hard workers and "default workers" who work as much as they're told to work, then do other things, some of which you just mentioned. Many people already find vaguely unjust, though it isn't.