Not everyone that has disc disease necessarily needs spinal decompression. In fact, most of the time conventional treatments such as chiropractic can offer favorable outcomes for herniated discs...either in the neck...or the low back.
It's the patients with herniated discs that don't respond to conventional back or neck pain treatments that become spinal decompression candidates.
For different reasons, the herniated or bulging spinal discs become positioned in such a way that they do not respond to various treatments. And, if the cervical or lumbar spinal disc is putting pressure on the spinal cord or a nerve root...the pain can be unbearable.