The most important thing is protecting them against harm, not disease... this can include knowing which vaccines might do more harm than good for your cat.
Most feline experts do not recommend the FIV vaccine at this time as it is relatively new and has its problems, not to mention that the disease is pretty uncommon in the US at least. Any cat that has received the vaccine will test positive for FIV, so if it is ever lost and picked up by animal control, it is likely to be destroyed as a FIV positive cat. Also, the vaccine only protects 50-70% of cats that receive it, so a cat can actually get the virus after getting the vaccine... but since it is already testing positive, how would you know? Also, like the FeLV vaccine, the FIV vaccine contains adjuvants, which are implicated in causing vaccine-associated fibrosarcoma.
FeLV is DEFINITELY a vaccine I recommend for most cats, particularly since my grandmother's cat died of FeLV, but if your cat is indoor-only and is never exposed to other cats, realistically, there's no reason for the cat to get it and you'll be avoiding the 1 in 1,000 chance of fibrosarcoma by not getting it for your cat. FeLV can't be carried in on your shoes or anything like some other viruses, your cat would have to be in contact with another infected animal to get it. Seeing as siamese are high risk for vaccine-associated fibrosarcoma and hoppybunn's cat is indeed indoor-only, I think the vet/breeder made a wise decision.