I was under the impression that in the US, paid vacation days were a bonus at the workplace. So in that case the people receiving this have just been smarter when they were in the bosses office discussing pay raises and other bonusses.
I mean, not everybody gets the same pay for the same function as well right? So why should this be different? But I'm not an American so don't take my answer as advice.
His fault for never inquiring about something he is legally entitled to anyway?
The Fair Labor Standards Act (FLSA) does not require payment for time not worked, such as vacations, sick leave or federal or other holidays. These benefits are matters of agreement between an employer and an employee (or the employee's representative).