Why do so many people choose to continue with chiropractic care long after their symptoms have disappeared?

They do it for the same reason they see their dentist twice a year. They like to maintain healthy teeth, and they want to give the same advantage to their spines. Keep in mind that your spine can decay just like your teeth.  Unfortunately, there's no such thing as dentures for your spine.

Daily stresses and traumas can cause the bones of our spines to stop moving as fluidly as they should (this is called the subluxation). If the spinal bones stay this way, and we don't have the problem corrected, the body jumps into a "use it or lose it" mode.  If you've lost spinal motion, the disc between the vertebrae (the shock absorber) begins to deteriorate. In a sense, it is forced to deteriorate. The disc gets its nutrition and expels waste through the natural motions and movements that occur in the spine as we move around. If you've lost the motion, you've lost the nutrition.  Without nutrition, the disc will deteriorate and die, just like anything else that isn't fed properly.

We like to use the graphic below to demonstrate the benefits of proper chiropractic care. The spine on the left is that of a 49 year old who has not given his spine the care it needs. At some point he lost motion in the joints of his lower cervical spine (neck). Having not sought proper care to return those joints to a normal state of fluid motion, they have begun to deteriorate.

Eventually these bones will totally fuse together. This person will lose the flexibility that they should have in their spine, and may end up with serious complications because of the delicate nerves that will be affected as the spine deteriorates around them. All of this might have been prevented if given the attention it needed.