Shots?

I need advice on shots for my cat.

The vet routinely administers the following shots annually:
FELV Feline Leukemia
FIP Feline Infectious Paratinitus
FIV Feline Immune Virus (cat AIDS)
FVRCP/C Feline distemper

He also administers rabies shots at the same time.

I went ahead with the rabies shot because it is required by law. I
postponed all other shots until I could find out more about them.

Clearly they are not necessary, but are they desirable, and if so on
what basis?

Let me try to summarize my uneasiness. The feline leukemia brochure
discloses that this vaccination does not always prevent leukemia. Now it
seems to me that there is some risk to a small animal in shots like
this, so how does the less-than-certain benefit of this shot outweigh
the risk of giving the shot?

In other words if there is a definite, significant benefit, then fine,
my little guy gets the shots. But if the benefit isn't definite, or
isn't significant, then I'm inclined to spare him.

What I'm getting at is that once upon a time it was sincerely believed
that tonsilectomies were a good idea for humans. Many infants had their
tonsils removed as a matter of course. Far too many. But it turns out,
it was not a good idea, especially not as a preventive measure.
Tonsilectomies are no longer performed except for good reason.

I mistrust serious procedures performed as a matter of course. Shots for
small animals are serious. The vaccines themselves are poisonous and may
have adverse consequences.

So I'm looking for explanations, shot by shot. Benefits if any, and how
significant? Risk if any, and how serious? Adverse effects, and how
would I know?

In case it helps, the little guy is a neutered domestic shorthair, and
mostly an outdoor cat. He is about 1-1/2 years old, alert and in good
health.

Thanks in advance

--
Jim