At least they have a flow activity betting. You should take a look at the bright sight, do you think they will always winning? no the user need to be lucky 50-100x meanwhile casino only needs lucky 1x until the user deposits more money. User who come to other casino from their favorite casino is always attract for the bonus first. If they not attract by the bonus, it's hard to make them move.
Are you saying this because you have done a study on the subject? There will be some who will just do what you say, while others will try the site and stay. It is well known that giving promotions and free stuff increases the clientele and the revenue in the medium term, and if MW has made this move surely they have studied it, although as in any business move you could be wrong but I don't think so.