I'm not saying this is always the case, but we never fixed my dog. He's a Chihuahua shizu cross. He developed a pernial hernia at age 12 and had an enlarged prostate. Our vet told us had we fixed him it wouldn't have happened.
So he had to go through an invasive hernia surgery that took 2 hours instead to save him from developing necrosis. He's now 14 and the hernia has come back(due to him having cluster seizures) and we have to watch it carefully and eventually if it becomes worse we will have to put him down.
If he had been fixed when he was 6 months we could have avoided all of this :( Fixing can be very beneficial to the health of a pet.
But that is the owner's personal decision, and it's not like it will happen to EVERY unfixed dog. I also know someone who didn't spay their cat and she developed ovarian cancer and died at age 5. Total anecdotal evidence but I spay and neuter since I have no intention of breeding them. If you plan to breed them obviously it would be stupid.
I do however think docking tails and reshaping ears IS unethical. If there is no medical reason for a surgery except human aesthetics that is pretty gross. Would people put their children through cosmetic surgery? Sure humans and dogs aren't the same but it's still messed up.