I don't think that's even a good type of business for the insurance companies. For sure if someone has a gambling insurance, that gambler won't be scared of losing anymore as there's a backup that he can get money again.
Even if it's just one or two claims per year, that would be a lot of money for the insurance company and they'll for sure be abused by those gamblers that would find them as a back up.
It's not just about the privacy issue but also about the insurance company itself that could go bankrupt too quick if there are too many claims.

I do not think that this is a bad business, rather there is no demand for it. For example, I am ready to insure anyone against gambling (and make an insurance payment much more often than twice a year), but it is unlikely that anyone will buy insurance from me, because I will not sell it to my own detriment, right? The business must be profitable, so I am ready to insure anyone for any amount, but the cost of insurance will be equal to the cost of the insured bet + 10%. That is, if you want to insure $100, then I am ready to do it for $110. It is unlikely that there will be many who want to buy such insurance
