The way I see it at UPS, is they try to get rid of you, before the bennies kick in after a year, or before your pension is vested in after 2 years.
They will make life misrable for you, that you would want to quit, or they find something silly to fire you.
Besides, they rather pay newbies the starting wage and no bennies, than any oldtimers. Much cheaper that way.
Numbers are numbers, and UPS goes by them daily, actually every second !