Okay, but (most?) many dentists are recommending scaling and root planing on a routine six-month basis for every patient in their chair. Some of those patients don't need it.
While those procedures are generally considered safe, there are risks, right? So, some people are being exposed to unnecessary risk (and expense). They are suffering from the over-interventionism I mentioned above.
There are legitimate risks that the dentist (or doctor) might miss something if they don't see you regularly. That's true. We've got to acknowledge the other side of the equation as well. The human body is complex. There are times when it is not black and white. Today, when a medical professional is presented with one of these situations, they err on the side of intervention. Add to this defensive nature of modern medicine the fact that there is little or no revenue generated by the wait and see approach.
Intervention pays. And it costs. Often more than money.
Tangentially related: I'm planning a Mt. Whitney trip and went to hear an expert speak on the logistics of the climb at a local outdoor shop. Turns out the expert was Dr. Ken Murray, professor of medicine at USC who wrote the now famous paper, How Doctors Die, which was shortlisted for a Pulitzer.
Physicians, it seems, seek medical care - especially end of life care - far less frequently than the average patient.
The article was considered groundbreaking for the simple reason that it was an emperor himself saying out loud that the emperor has no clothes.