Bonus is not meant to become profitable to the casino. They are gambling on the marketing hoping that they will attract more users but that doesn’t that a player conversion is guaranteed.
They are some sort of profits to the casino in the end because they are getting more bets from you by providing these bonuses.They have marketing expense but also gain a lot from it in the end and for players also if they get some good wins out of it they are happy for it.
Apart from marketing to attract new users and for the friendliness that the casino provides in giving bonuses it is also intended to keep its users loyal and enthusiastic about increasing their bet amount, it is just a strategy that casinos do to make gamblers with services like it makes them feel comfortable.
I myself feel happy when I get a bonus from what I have bet on, whether I have won or lost before.
With the amount of casinos that are around, all casinos need to do something and offer promotions, bonuses, contests, … You always need to trigger the interest of the people to not only attract new players but also, and more importantly, retain your old players.
I agree with you, basically bonuses have many classifications for both new users and old users, such as cashback or VIP rank bonuses, that will make players interested in staying at the gambling and visiting it every week or even every day.