Delate all accounts on gambling sites
Even though you suggestion is short,but for me,this is the good advice for those who wan to quit gambling.
How it can be a good advice as long as we can instantly create new gambling accounts at free of cost. Even if we close accounts, we can create them back whenever we want to gamble again. I do not think it is a permanent solution.
Maybe there are a lot of work to do for deleting our account on all gambling site that we already involve because we need to contact their admin for deleting our account on their site.But this method is good.
I do not think that gambling sites are supporting deleting accounts as just abandoning it will not harm anyone. Instead of requesting deleting, just changing the password and forgetting it (by not saving) will serve the purpose.