Leftover customs from agricultural society, that have become subconscious moralistic norms. If you sleep the daylight hours away on the farm, you will get less productive work done. After ten generations of this, there will be unspoken and unconscious rules about what sort of sleep schedules are acceptable. These don't go away by themselves.
Farming isn't and never was, the only occupation in the world.
So, simple solution - Don't be a farmer. Be a night guard or something.
This is really like the kind of problem we have today. We only have some 5 most popular professions in the world, so people are rigged to cater to the customs of these 5 professions. Everyone else is just "lazy"!
Historically a much greater portion of the population was involved with agriculture (75% of the working population)[1] at a time when artificial light was both relatively poor quality and very expensive.
Given those constraints it makes sense that there was massive societal pressure to maximize the hours the sun did shine. Looking at the charts on that site also brought home how relatively recent the shift to non farm based employment really was (a couple generations). Even that probably fails to account for large behavioral changes: for example my great grandparents had a "garden" that was at least an order of magnitude larger than any suburban garden I've seen in the last decade. They weren't "farmers", just poor and the extra food they grew and canned was a huge help.
