The cash payout percentage varies depending on the level of interest rates. What happens if the interest rates go to 0%. Will that mean the cash value is equal to the advertised jackpot?
Interest rates - or rather, rates of return - vary between investments. If one investment's rate drops too low, the company selling the annuity to the lottery will pick other investments. If all the rates drop to zero, two things will happen: the advertised jackpot will be the cash value, and the world economy will collapse.