Is this widely known? Presumably the jackpots are sufficiently geographically distributed so that a player who observes one wouldn't be incentivised to pause playing?
These are probably the kind of machines you sometimes see in gas stations and bars, there's only a few of them in any location at most so there's never too many players nearby to be dissuaded from playing. Plus, a jackpot isn't the only way to win money.
I don't think it is widely known how much casino gaming machines are allowed to control outcome. Indeed, in some cases they are required by law to control outcome.