There is concern about the two, but different levels of importance placed, I think. The data they hold and risk losing is more important to gamblers than the money the money they have, and then to the casino, I believe it will be that they have more importance to the money than the data of the many gamblers. Now based on this, do you feel a casino is more likely to be careless with people's data than they will with money to hackers because most hacks seem to target money they have more?
Online casinos should implement more verification levels for logging in, such as facial authentication before accessing the account, this way it will become almost impossible for the hackers to gain access to the gambler accounts unless in case of extreme internal actors carrying out the hacking. If casinos have placed importance on KYC verifications as a mandatory demand that gives out customers' Data to them, they must come up with development and system that protects users' data 100% this is because hackers if allowed to get a hold of those verification documents, it will become a dangerous thing altogether for gamblers who lost their data in the case of a hack.
As there are now sophisticated hacking softwares, casinos should make sure they have enough allocation when it comes to their security features. They are holding valuable data as well as funds from their customers. One loophole and their business is gone. Hence, for me, it is a big deal for me when you deal with security aspect of the business. Hackers will try again and again up until they see the vulnerability of the site. After all, that's their job, right?