Some people always get this wrong, not everything is relating to a spiritual issue especially gambling, it's more relating to a mental issue than something spiritual for instance you shouldn't be referring an addicted gambler to the church or spiritual home for prayers, rather such cases should be handled by a mental health practitioner, psychologist or the rightful professionals to handle the situation, your spiritual leader or teacher is just a religious leader meant to handle spiritual cases and not the right one to handle such cases, I don't know about other societies but I've seen people in my region make such errors and it needs to be addressed.
How sure are you that some addiction are not spirit driven? Well it could be that most of this addiction is caused by human behavior, but don't also forget that some are driven by spirit, expecialy ancestral causes that is pass down from generation to generation. so you can't just judge. I believe you are talking from your own level of understanding.
I agree with you that a person who is a gambling addict doesn't need prayer but counseling, but don't also forget that there is nothing too hard for God to do.