I ask again who is to blame for the increase in bonus abuse, the customers/fraudsters or the online gambling operators?
There is no way fraudsters can be blamed in a case like this, the gambling operators are the ones to be blamed.
It is true that fraudsters can become so tech-savvy that it seems they can create a loophole where there was non, but there is a saying that, when the bird learns to fly without perching, the hunter will learn to shot without missing....
You are talking about the law of the jungle but we are not in that state. There are laws about theft, abuse and exploits and they are illegal. What those players/exploiter do was to rob the casino because they saw an openning.
It's as simple as that, gambling operators are the ones to blame for not putting their house in full order before inviting the general public, when your house is not in order and you invite the general public to come and feast with you, there is a high chance that many of your items will go missing even before the feast is over.
So it is also with gambling Operators who open their doors to customers when they have not done or passed all security checked.
You are saying, it is ok to shoplift because the store had put their item in the open. Remember lots of casinos have multi-account restrictions, exploit restrictions, and bug abuse restrictions. If someone signed up with the casino, they all agree with it. Anyone exploiting, bug abusing, and multi-accounting just to exploit the open hole the company left is the same as a civil case because that is obviously a breach of contract and possibly face a criminal lawsuit called larcerny/grand larcerny.[1]
larceny
noun
theft of personal property.
grand larceny
(in many US states and formerly in Britain) theft of personal property having a value above a legally specified amount.
[1]
https://www.avvo.com/legal-answers/if-i-abuse-a-casino-s-bonus-system-and-make-thousa-5437243.html