I think the marketing strategy some casino used to lure customer more to their casino is these free bonuses, you would be suprised how it works but human and gamblers as a whole have a way to go about their greed and ego sometimes they get traps in all these free bonuses and turn out to game more on the casino. Every gambler is searching for an atmosphere where they will feel they have an edge over and making yours similar to what they are looking for will give an advantage.
People have their minds to read, assess information including any marketing program, and .are their decisions to join or ignore a program. It is not like a gambling site tries to lure or set up traps to get money from users.
Users are free to consider carefully on how good a marketing program is as well as how they can manage their gambling activities for meeting criteria of a program and enjoy given benefit from it. If they are not experienced enough, the company can not force any people joining so no reason to blame anything.
Even a very good investment asset like Bitcoin that has absolutely amazing ROI over many years, there are still many people lose money in Bitcoin market. However let's be clear that it is not responsibility of Bitcoin on loss of any market participants.
I support what you said about users been free to consider their decision carefully before they participate in a certain bonus event, since every bonus event havee it rules and regulations which are always stated clearly.
The area of casino using the bonus event to lure gamblers is what I dont agree with because one of the cateria most gamblers always look at before using a casino is if the constantly have bonus event, so when a casino gives gamblers what they want that shouldnt be consider as a means lure them in unless if the provided rules for the bonus is unfair.