I think the emphasis is on getting the most labor done during daylight hours more than anything. Easier to start jackhammering at dawn than to risk having to cut the job short by dusk. tough to harvest crops at night too.
If that was true, it would be different in winter, but it isn't (at least for big projects). I've had a lot of renovation projects done, and all the trade folks I dealt with just like having most of their afternoon free, by starting super early. The jack hammers across the street will start in pitch darkness, they'll just use powerful lights.
