I worked as a vet tech for 7 years, and these vaccine related tumors were just becoming an issue while I was working. I completely agree with strictly indoor cats not necessarily needing their boosters for distemper (and definitely not for leukemia) every year after they receive their kitten shots, but even if I had indoor cats they would always be vaccinated for rabies because of experiences I have had and the strict laws regarding rabies. There is a "Purevax" rabies vaccine which was created to be less likely to cause these tumors because it does not have the preservatives that they believe may cause them. It is only good for 1 year, as opposed to the 2-3 years that the other rabies vaccines are good for. My 2 cats have been receiving this rabies vaccine for several years now, in their rear legs so the leg could be amputated if they ever did develop a tumor. Of course, my cats get distemper and leukemia every year also, since they are indoor/outdoor cats (we live on 400 acres on a quiet dirt road).
I have had bats get into my house at night several times, and I know other people it has happened to, even in more urban/suburban areas than where we live. You also never know when anything else could happen, like a cat slipping out the door and getting into a fight. One of the times a bat was in the house, we had a puppy who had not been vaccinated for rabies yet because of his age. Because we could not be sure whether he had interacted with the bat at all, we had to have the bat tested for rabies, and if it had come back positive the puppy would have needed to be quarantined in a shelter at our expense for 6 months to make sure he did not develop rabies. Fortunately, the bat was negative. I keep my cats vaccinated for rabies according to state law because I don't want the worry of putting them to sleep or quarantining them if something unexpected happens.