Because you're not an hourly worker. Your job doesn't involve punching in a time clock, so there is no such thing as overtime. The flip side of this is there's

Because you're not an hourly worker. Your job doesn't involve punching in a time clock, so there is no such thing as overtime. The flip side of this is there's no such thing as undertime either. If you go home early one day, you still get paid for the full day.