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?
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.
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.