This can even be true when you show the client gum lesions that are exuding pus. Guaranteed if you showed them lesions exuding pus anywhere else on the body they would be horrified. They would expect immediate curative action. But not so for the teeth.
Why is this?
In part it is because the teeth are generally not visible. That being said, I would like to note that sometimes the same people will then go on to show me a minuscule lump somewhere deep in the dog's groin or be genuinely concerned when blood tests reveal a more minor issue in an internal organ that is definitely not visible.
Another factor is that animals do not show dental pain. This sometimes results in the reverse problem wherein the client will absolutely insist the cat isn't eating because his teeth are bad. There are 968 common reasons for a cat not to eat and that is not one of them. It is a very uncommon reason for them not to eat. But the pain question is also only a partial answer as many other conditions that are not painful elicit far more interest from the dental skeptical clients.
So then, what is my theory?
My theory is that we must blame the weird history of the human dental profession. Objectively speaking teeth are part of your body. Actually, subjectively too. Teeth are part of your body: objectively, subjectively, factually. Agreed? Why then is it the only part of your body to have an entirely separate profession devoted to its care? It turns out to merely be an accident of history. We could have just as logically ended up with a separate profession focused on our fingers and toes. "I'm off to the digitist dear!"
Before the 20th century there was a division between physicians who examined sick people and prescribed primarily quack remedies and "barber surgeons" who used their sharp razors and steady hands to perform surgeries ranging from lancing boils to amputating limbs as a sideline between hair appointments. Some also had a set of pliers handy to pull teeth (as did some blacksmiths). That was the sum total of historical dentistry - yanking festering molars. Carpenters and other tradesmen made false teeth. As regulations began to gel the more ambitious of the razor wielding barber surgeons craved the prestige the physicians enjoyed and those professions gradually merged, more or less accidentally leaving tooth pulling behind and unregulated. Later on the medical colleges who began to shut down all manner of other trades that were "practicing medicine without a license" (midwives come to mind) ignored the tooth pullers because they didn't seem to be a threat and, some will darkly say, because they were of similar social backgrounds.
This has left us with a situation where in Canada medicare will pay to operate on your infected toe, but not to operate on your infected tooth. A situation where you have two incompatible sets of records regarding your health. A situation where some people see their teeth as being divorced from the big picture of their health. Arbitrary and weird. Dentistry is weird.
And for us poor veterinarians who have successfully kept the entire body of our patients under one umbrella, it is a situation where some pet owners have a different mental box for teeth than for the rest of Fido/Fluffy's body.
p.s. My dentist is great and not all that weird. I just think if he were an MD dental specialist my life as a veterinarian would be simpler.