In this Los Angeles Times article Joe Robinson explains why paid time-off (PTO) banks are another way risk is being shifted from the employers to the employed:

"Paid time-off banks combine sick leave and vacation days, creating what at first looks like a jackpot — extra vacation days and more flexibility. But the winnings are subject to the vagaries of chance — your health — and corporate sleight of hand. Once your sick days are used up, further absences not covered by short-term disability come out of your holiday hide . . . American workers who have used up their puny sick-day allotment will have to decide whether to stumble to work sick or stay home and burn up vacation days. Or worry that if they roll the dice and take time off, it could jeopardize a paycheck if a health emergency hits. It adds another layer of guilt to gobs already there in taking a vacation, making it seem selfish to squander days that might be needed if you or a family member get sick."