Bonuses can garner potential players for a casino. It can make someone stay, sure, if that's the thing about a casino that a player is very particular with. But I think the overall quality of service, games, and processes in the website are what will make a gambler loyal to the casino. This is because no matter how frequent a casino gives bonuses and no matter how big the amount of the bonus is, if the process of withdrawal of it will be a big hassle, the effort and time exerted will all just be put into waste.
Yep if there's many problems on the withdrawal, it's a red flag where the casino is actually doesn't have enough bankroll to pay all of their gamblers winnings. I think you and many users in this forum know there's a casino that has a problem with their withdrawal everyday and then it's turn become a scam casino where they abandon their project. Many promotions are very good, but the developer need to consider about the management risk and their bankroll.