This is like saying that once you are a rich person you don't need to work for money anymore, but in reality if you are a billionaire you will stay billionaire with your nonstop income stream, no rich person will ever say no to extra, and also no amount of money will ever be enough for rich people.
Casinos are mostly profitable, it's one of the most lucrative business I know and selling shares isn't a bad idea, it brings more money anyways, there is no business that's too big for shares, there are too many examples of giant companies around the world that has shares, they made insane amount of money every week yet there shares are out there floating. I will accept that shares is a choice, for casinos but big and small it doesn't make a difference.
And what is so extra about them giving a share of their huge pie?
Big casinos make BILLIONS of dollars. So you think they should "sell shares" where small investors gives them money they don't need (because they already have billions) so they share a part of the profit that they could keep for themselves? Besides all the legal hassle which is a nightmare.

When you say companies around the world have shares, you're talking about public companies. You should probably read more about it:
https://investingbrokers.com/why-do-companies-go-public/