> I often wonder why there isn’t a great movement toward a reduction in working days/hours in the modern workplace.

There are voices saying that. You can find some on almost every HN thread about work. This is a tricky topic, though, because our society has a deeply ingrained sense of deriving one's self-worth and status from the job they perform. A sentiment that was once critical to our survival - now, arguably, less so.

> Modern society should be solving for this.

There are attempts. 4-hour workweek. People (like myself) switching to remote work to reclaim time spent commuting. Individuals seeking FU money. Proposals of UBI. Regulations around paid vacations and parental leave. It's messy and slow-going, and things probably won't change until there is a cultural shift in our relationship with work we do.