Both of them had a high concentration of spiritual essence, and they were both secluded locations.
The difference was that Cave Abodes often existed in alternate spaces with peaceful spiritual essence. Most of them didn't have living beings inside.
Even if there was, the threat was negligible.
Therefore, Cave Abodes were often transformed into places like sects or academies by cultivator masters and mighty figures at a high price.
However, the spirit cave was different.
Most spirit caves existed in the form of caves and catacombs, and spiritual essence was relatively active. Cultivators couldn't absorb it passively, so they had to absorb it voluntarily.
Also, there were a lot of spiritual essence-induced creatures in spirit caves.
These spirit monsters were hot-tempered and would attack all non-spirit monsters that entered the spirit cave.
Because of that, spirit caves were often not feasible to modify.
