I think Limitations on game options: If there are fewer game options for players to choose from, the interest towards the game may decrease, leading to lower participation and the jackpot growing at a slower pace.
Jackpot limitations: The rules of the game could have a cap on the amount that a progressive jackpot can reach, which means that the jackpot will stop growing once it reaches that limit.
Jackpot limitations: The rules of the game could have a cap on the amount that a progressive jackpot can reach, which means that the jackpot will stop growing once it reaches that limit.