Of course, they want everyone to know that a jackpot has been won in their institution and this should attract additional attention to such an institution. And this is at odds with the desire of those who have won a significant amount of money and do not want to attract attention to themselves, because they may become the object of robbery or extortion.
That robbery aspect is the disadvantage of such a move; the winner becomes a target. You can't tell who will follow him or her down to their house to rob them of that money. We have seen a lot of such cases here in the forum, and it's very dangerous.
There are better ways of telling other gamblers that a big win has happened here for sports betting here in my country, and such games always have a booking number that anyone can check online; even when you don't log in, they can always display such a ticket number on the display screen and on their site, and people will see that such an amount was won instead of endangering someone's life where they are looking for means to retain their customers.