Assuming an 8 hour work day and no drop in worker efficiency, the two extra work days would increase the labor supply by at least 40%.
This could have come about from a society which has a great need for human labor. Possibilities include...
- A very low population density.
- Energy starved, so human labor is cheaper than machines.
- No industrial revolution, so no labor saving devices.
There could be an external or internal threat which makes it necessary to maximize production. War, famine, disease... take your pick.
If the society is industrialized they have less need for labor, so increasing the labor pool would lead to unemployment or make-work. In that case, this becomes a distopean "make work" program. Reasons include...
- A fanatical work ethic.
- A "keep the masses busy" repression scheme.
- Bureaucratic inefficiencies gone wild (a la the movie Brazil).
With everyone working eight hours every day, sleeping eight hours every day, and having to recover from work every day there's greatly reduced time for a personal life. This restricts personal and economic possibilities.
Nobody can travel more than a few hours from work. No family vacations. No trips to a foreign country. People will stay at home. Long distance travel will all be for business. Out of town tourism will be almost non-existent. People will rarely leave their home area. Everything will be more provincial in nature.
Every personal project must be able to be broken up into eight hour chunks. Aside from the obvious problems with your personal life, there would be numerous problems for entrepreneurs. There is less time off to investigate starting a new business or learning a new craft or tinkering with an invention.
To accommodate total employment, if the society has good lighting, things would not be left idle at night. There would likely be work shifts around the clock. This would create a 24 hour society.
With no holidays, and a 24 hour society, there's no infrastructure downtime for repairs and maintenance. Repairs and upgrades would regularly interfere with the constant flow of people, information and goods. Infrastructure would have to be made extra redundant so it can be taken down for repairs and inspection.
Entertainment would shift towards what can be done quickly and easily by people physically or mentally exhausted by work every day. Drinking, drugs, and passive entertainment (watching professional sports, TV, and movies) would be the norm.