Gamblers may be suspicious but actual frauds means you. Red to trap the site owner only. They were introducing which is not legal in your country so you must be careful before you invested on any gambling sites.
Criminals in gambling field? I don't vote for it for sure.
Maximum people invested on gambling must clear the way they are moving for earning purposes.
It is true that people come to gambling site for the purpose of money making but we need money to bet on the gambling sites which may tempt the people to do crimes to get that money and even when they are addicted they can do anything to gamble but it is very rare case thoug.
Gradually gambling leads to crimes. In my country gambling is not legal and I myself do not believe in online gambling because there are many scammers and fraud as you mentioned. Anyway for gambling online or traditional you need money and when you have no money for gambling and face money problems you will do anything to get some money for gambling.