I never understood why my declawed indoor cats had to have rabies vaccinations
Rabies is different from the other vaccinations since it's a human public health issue, and in many places vaccination is the law. (I just checked on line - this is true in Pennsylvania, as it is in Connecticut and Massachusetts where I've lived.) Your cat COULD get out. Its circumstances could change - people do abandon declawed cats. I'm not saying you would. But the vet can't just take your word for it, much as YOU know you'll keep your cat always (and have provided for your cat in the event taht you're hit by a bus or your plane falls out of the sky). And if it's the law in your state, how would YOU write a law that says all cats and dogs must be vaccinated - EXCEPT those kept always indoors and owned by really, really responsible people? (In practice, since cats aren't generally licensed, if you don't vaccinate you won't be hassled unless your cat bites someone and probably no one will bother to follow up even then. But vets are aware of the possiblity of rabies out there, and the law if that's the case in your state. And the fact that no one's checking the vaccination status of the cats that are outside is actually *more* reason to make sure that all possible cats are vaccinated when the vet sees them.)
I was just in China. It's a shock to be told not to go anywhere any dogs or cats you see because rabies exists there, not just in wild animals, but in people's companions, because people can't all vaccinate their pets so there's a reservoir of virus out there.
Feline leukemia is a different issue - on my cats that stay in (by choice), including the one who does go out occasionally to sit on the porch, I've discontinued that one by choice with no peep from my vet. Does yours object? I'm surprised.