Although as someone pointed out above, if the doctor gets the results in the morning because the bloods were taken overnight, they might be able to discharge the patient immediately and get a bed before lunchtime for another patient. If they wait to take bloods in the morning, the patient might be in another day for no particular reason.
Five years ago in Switzerland I could get a full blood panel from my Dr's office in the mall within twenty minutes. The blood came straight out of my arm, into the vials, and into vials went into the analysis unit.
Maybe there needs to be some investment in better analysis equipment for routine draws.