most of the time they are attracted for some sort of bonus or rewards. as this site has no thread in the forum, high chance that his case will not be resolved. also, this should be in the scam accusations board so he can warn other users also. for most gamblers in the forum, they know where to get the info they need before they spend money to the casino. and actually, this is the main board for gamblers here.
if the offer is too-good-to-be-true, doubt their intentions.
My two reasons why I would not sign up to a casino, casino do not have a thread here so no way to report or a chance for them to answer my allegations, second you are right in your opinion if the offer is too good to be true doubt their intentions, the only time they can offer big bonus is when they are launching and it should be very limited time or they are in their anniversary week and also in a limited time, any more than that it's not good.