Not only gambling casinos but also in exchange platforms as well as long a site does have lots of funds involved then they are really that susceptible from hack because they do know that this is the sweetest spot on
finding out vulnerabilities and loop holes which they could really able to steal websites funds  specially on hot wallet but we know that not all casinos does store all of funds on a hot wallet but also
into their cold storage to prevent out completely wipe of funds which is very common behavior for platforms like these.