One vet I spoke to said that heart worm was not much of an issue for cats. I do think that some vet practices use the immunization schedules to their advantage to get the animals in for the yearly immunizations to pad the profit margins. For instance: giving the yearly rabies vaccine when there's a 3 year one available, and giving the whole litany of vaccines to the cat who never goes out.
I agree. We can get the 3 year for dogs if they gad the one year peior. But cats. Ugh. They need and annual, and if they are not utd on that, then no flea meds.