As someone who is exposed to gambling and the casino ecosystem, I like to know if you would prefer to be a game owner or provider who has his game on different casinos or you prefer to be a casino owner who has different games featured on your casino?
Which of them do you think there will be more profit in?
There is no way an ordinary dev would profit from a business more than the business owner himself, owning a casino is a business, while being a client or developer is just a contract, you make money on the royalty or subscriptions on your game and nothing else, worse still if your game was purchased on a one-time purchase, then you earn once and the casino owner keeps profiting from your game on his platform.
The duty of the casino owner is to manage his workers and invest in marketing and drive more clients to the casino which you and I know that there are numerous gamblers and as little as an enticing welcome bonus can lure people into patronizing you and remaining loyal if your services are good and your website user friendly.
The casino owner is nowhere comparable in profits with the ordinary game developer and most times they are even employees of the casino, even if the game dev is a shareholder in the casino company, he doesn't even come close to profits compared to the casino owner.