That's simply not true. In some hourly paid positions in some locales, there are mandated overtime pay rates, but salaried employees have no per-day hour maximums.
The fact is that employers don't work their employees 16 hours per day because it's counterproductive and employees would go find employers who didn't work them so hard if they tried.
Well, history says different, and how things actually happened tends to have more weight than theoretical speculation about a perfect employment market.
The fact is that employers don't work their employees 16 hours per day because it's counterproductive and employees would go find employers who didn't work them so hard if they tried.