That's if they can last the 5 years it can take to become vested in a company for matching 401k benefits and those extra earned vacation days which become a liability to the company when they have to lay people off.
No, they'd rather periodically dump and rehire employees rather than permitting them to establish a compensated history at the company.
The CEO of EchoStar waspublicly quoted as saying that he wanted turnover to prevent seniority and the pay that comes with it.
It's just like the NFL when they release veteran players to save money against the salary cap.