Hi N.,
I work for a small animal veterinarian and can honestly tell you that there are many reasons why a veterinarian may or may not suggest a certain treatment. We have several hyperthyroid felines in our practice, and not one has ever been suggested to undergo iodine treatment. While many see fantastic results with the treatment, it is expensive and risky. There is no guarantee that your cat will still no longer require medication post-treatment and it is radioactive and that of course comes with its own set of risk factors, requiring quarantine period and it is often only done in specialty clinics with vets/techs with extensive training...which may not have been available until recently in your area or by your vet. The treatment itself is not new, however, I know the vet I work for will not recommend something until he has seen the results over a period of time and feels confident it is safe enough to suggest. (including less-risky products such as new flea/heartworm treatments- everything comes with its own potential side effects) Additionally, while you may be able to afford or consider the cost of treatment, many people think twice before spending $1,000 or more to treat a cat and this procedure is often seen as a last resort.
I commend you on being proactive on researching treatment and for treating your feline friend...I know giving medications daily is a commitment and frustration in and of itself, and hope you do see the right results with on-going treatment. I wish you the best with your kitty!