Just as an example of how companies like to use Salaried positions to gain extra work from employees, without extra pay. For this example, we'll be assuming the company is retail, simply to keep it easy.
the math should be easy to follow:
Employee A gets a position as a cashier. Pay is $20/hour. Set schedule, 40 hours a week, 52 weeks a year. Annual income? $41,600.
Employee B gets a position as assistant manager. Pay is salary, annual payout, $70,000 a year. Overtime is listed as required but rare, otherwise, 40 hour a week based salary.
Now's where it gets fun: Employee A never gets a single second of overtime. Their annual salary of $41,600 is based on 2080 hours worked. Their breakdown for hourly is literally the $20 they agreed to. Employee B finds out that "rare" on overtime means they consistently work 70 hours a week. Their $70,000 annual salary is unaffected by the increased hour requirement.
So, the Assistant Manager, employee B, is putting in 70*52=3640 hours a year. That boils down to 70,000/3640=$19.23/hour.
Funny thing is, if the company is short staffed on cashiers, will the cashier be given the opportunity for overtime? Not a chance. That's what the assistant is for.
Now here's where it gets really fun: Let's say employee A DID get the overtime, and work that same 70 hour week that the employee B does. Okay, so you're looking at 2080 hours at $20 ($41,600), 1560 hours at $30 ($46,800). Total annual income? $88,400.
The company uses the promise of higher pay to attract the person to ther salaried position, then forces them to work a number of hours that reduces their actual pay to below that of the hourly employee. They do it intentionally. Now, let's say the hourly employee, who's not getting overtime, gets a second job as a cashier elsewhere, that also pays that $20/hour, but this is a 30 hour a week position. Now we're back to 3640 hours*$20 an hour equates to an anual income of 72,800. Even WITHOUT OT pay increase, the cashier is more highly paid than the Assistant Manager AND they don't have to worry about randomly being called in or any other such disturbances to their lives.
People who promote these business practices designed directly to trick prospective employees into less pay for more hours while destroying their ability to take on a second job because of a constant "on call" status are garbage, and inappropriate in most fields.