In 1999, Apple decided to rewrite the Finder from scratch for Mac OS X, separating its user interface and core functionality. The backend, known as Finder_BE or Desktop Services, dealt with enumerating files, watching for changes, and managing metadata. The .DS_Store files created are essentially the “Desktop Services Store,” meant to be invisible to Unix OS. Unfortunately, a bug leads to excessive creation of these files, even when no adjustments are made. The Desktop Services API was planned to be made public, but it has not been fully released to this day. Overall, the origin of .DS_Store files and Desktop Services sheds light on Apple’s technical decisions and challenges.
https://www.arno.org/on-the-origins-of-ds-store