You can thank the Jews, the Christians, unions, Henry Ford, and the Great Depression.
When you start tracing the dependencies between organizations throughout the economy, you start seeing why having a widely shared set of shared working days and working hours actually makes quite a bit of sense from that perspective.
Obviously this sort of spread wouldn't work in every industry, but the idea that any "professional" should work from approximately 9-5 on M-F causes obvious lifestyle load balancing issues we could avoid by spreading it out much more were possible.
Maintaining sufficient overlap is partly a matter of individual schedule preferences, and it gets easier as amount of free time increases (though, obviously, at a cost of overlap in work time) and as scheduling flexibility generally increases. Currently, if my wife has a "9-5" and I am stuck working something with weekend shifts, my wife typically lacks the flexibility to shift her schedule to match mine. What I am most strongly arguing for is increased flexibility where it is feasible.