That is common but as you have noticed it is a mistake to think this way, bonuses can help to offset some of the losses you have sustained, and for the casinos this is one of their main purposes as they want to give something back to their loyal gamblers.
However if you try to gamble more than what you are used to just to get a bonus, then you are going to find out that instead of the bonus helping you it will play against you as your losses will be higher than if you did not chase the bonus.
Yes, it's true, as you said, because every casino will definitely make a way so that their customers feel benefited and can really become loyal customers.
In my opinion, a bonus that is a little more profitable is a bonus that is given to customers who have VIP accounts because that way customers can get bonuses every week instead. .
When compared to spending money to be able to get a bonus, I prefer to pursue a VIP level bonus rather than a deposit bonus or a minimum bet.