~snip~
I think OP is framing this question in a context where a person has ran out of options and traditional approaches had not given the expected results to control the problem gambling.
It is similar to those who may suffer from stress, for example, and after giving a try to pills and other kinds of medicine with limited results, they decide to go for meditation or oriental medicine, some things works, others do not. The important thing here is not to mix alternative medicine and treatments with quackery, there is where the danger is, in my humble opinion.
I would prefer the meditation option if I were a compulsive addict. be it a drug addict or a gambling addict. the meditation option, is more widely adopted than the hypnotic option in alternative fashions for curing addictions. however, as you said. for this type of alternative there are successful, some are not. and in my opinion, the same thing if we choose a place of rehabilitation. the fact is, some are cured, some are not. which in essence, every case of addicts has a different method of healing.
But in meditation mode, the positive impact will be better than the hopnotherapy method which is more identical to entering one's subconscious to give certain suggestions. and once again as you said, that the hypnotherapy method does not necessarily work for all gamblers. but if it's for meditation, the benefits we get are quite a lot, including balancing our souls and feelings. not only to let go of addiction, but the benefits that we get are more positive than hypnosis. one of them, healthy our minds.