With no cavities and the ability to brush my own teeth, why should I pay a dentist to clean them?
Even the most diligent brushers can’t clean every nook and crannie. That’s why dentists go to the dentist.
Also, your dentist may spot tooth and gum problems before you notice them, in which case they can probably be fixed in an easier way. Preventative maintenance, and all that.
A dentist (or dental hygienist) removes tartar, which tends to build up even if you brush and floss thoroughly. Tartar irritates the gums and can exacerbate gum disease.
Because he’s (hopefully) an expert at the task, which ought to mean he’ll do a better job of it than most people would do for themselves.
I’d say it depends on how old you are; how long you’ve gone without cavities. I had a cavity when I was 11. Since then I’ve been to the dentist in 1980 and 1997, and still have just the one cavity. My dad has a similar record: I often say the only good thing I ever got from my dad was granite teeth.
If you’re in the same situation, I wouldn’t worry about it too much.
You can’t do the scaling yourself; when the guy is scraping away especially on the back side of your teeth. You won’t be able to see there, probably don’t have the tools to do it if you could, and wouldn’t be able to do it very well with only one hand (the other holding the mirror). Also he/she can tell you if you’re doing your own cleaning properly - you might be missing and spot unknowingly.
And as has been said, the dentist looks into every little nook and cranny, and knows how to spot potential problems ahead of time… plus the X-rays too. Without that kind of early warning, you have to rely on pain to tell you something’s wrong, and by then it’s too late.
There are times when it is appropriate to see a professional. Having a relationship a dentist, if not even regularly, will at least give you some place to go if you do have a problem or an emergency. I look at it like this: I have pretty good teeth already. I’m ahead of the game and want to keep it that way.